diff --git a/mobly/base_test.py b/mobly/base_test.py
index cdd91c2b..78651ba8 100644
--- a/mobly/base_test.py
+++ b/mobly/base_test.py
@@ -34,8 +34,8 @@
 RESULT_LINE_TEMPLATE = TEST_CASE_TOKEN + ' %s %s'
 TEST_SELECTOR_REGEX_PREFIX = 're:'
 
-TEST_STAGE_BEGIN_LOG_TEMPLATE = '[{parent_token}]#{child_token} >>> BEGIN >>>'
-TEST_STAGE_END_LOG_TEMPLATE = '[{parent_token}]#{child_token} <<< END <<<'
+TEST_STAGE_BEGIN_LOG_TEMPLATE = '[%s]#%s >>> BEGIN >>>'
+TEST_STAGE_END_LOG_TEMPLATE = '[%s]#%s <<< END <<<'
 
 # Names of execution stages, in the order they happen during test runs.
 STAGE_NAME_PRE_RUN = 'pre_run'
@@ -195,10 +195,7 @@ def __init__(self, configs):
     self.tests = []
     class_identifier = self.__class__.__name__
     if configs.test_class_name_suffix:
-      class_identifier = '%s_%s' % (
-          class_identifier,
-          configs.test_class_name_suffix,
-      )
+      class_identifier = f'{class_identifier}_{configs.test_class_name_suffix}'
     if self.TAG is None:
       self.TAG = class_identifier
     # Set params.
@@ -257,7 +254,7 @@ def unpack_userparams(
         continue
       if name not in self.user_params:
         raise Error(
-            'Missing required user param "%s" in test configuration.' % name
+            f'Missing required user param "{name}" in test configuration.'
         )
       setattr(self, name, self.user_params[name])
     for name in opt_param_names:
@@ -509,19 +506,11 @@ def _log_test_stage(self, stage_name):
     # reference tag as the parent token instead.
     if parent_token == stage_name:
       parent_token = self.TAG
-    logging.debug(
-        TEST_STAGE_BEGIN_LOG_TEMPLATE.format(
-            parent_token=parent_token, child_token=stage_name
-        )
-    )
+    logging.debug(TEST_STAGE_BEGIN_LOG_TEMPLATE, parent_token, stage_name)
     try:
       yield
     finally:
-      logging.debug(
-          TEST_STAGE_END_LOG_TEMPLATE.format(
-              parent_token=parent_token, child_token=stage_name
-          )
-      )
+      logging.debug(TEST_STAGE_END_LOG_TEMPLATE, parent_token, stage_name)
 
   def _setup_test(self, test_name):
     """Proxy function to guarantee the base implementation of setup_test is
@@ -910,13 +899,12 @@ def generate_tests(self, test_logic, name_func, arg_sets, uid_func=None):
         is the corresponding UID.
     """
     self._assert_function_names_in_stack([STAGE_NAME_PRE_RUN])
-    root_msg = 'During test generation of "%s":' % test_logic.__name__
+    root_msg = f'During test generation of "{test_logic.__name__}":'
     for args in arg_sets:
       test_name = name_func(*args)
       if test_name in self.get_existing_test_names():
         raise Error(
-            '%s Test name "%s" already exists, cannot be duplicated!'
-            % (root_msg, test_name)
+            f'{root_msg} Test name "{test_name}" already exists, cannot be duplicated!'
         )
       test_func = functools.partial(test_logic, *args)
       # If the `test_logic` method is decorated by `retry` or `repeat`
@@ -1054,8 +1042,8 @@ def _get_regex_matching_test_methods(self, test_name_regex):
   def _assert_valid_test_name(self, test_name):
     if not test_name.startswith('test_'):
       raise Error(
-          'Test method name %s does not follow naming '
-          'convention test_*, abort.' % test_name
+          f'Test method name {test_name} does not follow naming '
+          'convention test_*, abort.'
       )
 
   def _skip_remaining_tests(self, exception):
@@ -1174,11 +1162,11 @@ def run(self, test_names=None):
           self.exec_one_test(test_name, test_method)
       return self.results
     except signals.TestAbortClass as e:
-      e.details = 'Test class aborted due to: %s' % e.details
+      e.details = f'Test class aborted due to: {e.details}'
       self._skip_remaining_tests(e)
       return self.results
     except signals.TestAbortAll as e:
-      e.details = 'All remaining tests aborted due to: %s' % e.details
+      e.details = f'All remaining tests aborted due to: {e.details}'
       self._skip_remaining_tests(e)
       # Piggy-back test results on this exception object so we don't lose
       # results from this test class.
diff --git a/mobly/controllers/android_device_lib/fastboot.py b/mobly/controllers/android_device_lib/fastboot.py
index 0591e206..35d07cbc 100644
--- a/mobly/controllers/android_device_lib/fastboot.py
+++ b/mobly/controllers/android_device_lib/fastboot.py
@@ -75,7 +75,7 @@ def __init__(self, serial=''):
 
   def fastboot_str(self):
     if self.serial:
-      return '{} -s {}'.format(FASTBOOT, self.serial)
+      return f'{FASTBOOT} -s {self.serial}'
     return FASTBOOT
 
   def _exec_fastboot_cmd(self, name, arg_str, timeout=DEFAULT_TIMEOUT_SEC):
diff --git a/mobly/controllers/android_device_lib/jsonrpc_client_base.py b/mobly/controllers/android_device_lib/jsonrpc_client_base.py
index d272782d..abdd8e72 100644
--- a/mobly/controllers/android_device_lib/jsonrpc_client_base.py
+++ b/mobly/controllers/android_device_lib/jsonrpc_client_base.py
@@ -211,9 +211,7 @@ def connect(self, uid=UNKNOWN_UID, cmd=JsonRpcCommand.INIT):
       # Retry using '127.0.0.1' for IPv4 enabled machines that only resolve
       # 'localhost' to '[::1]'.
       self.log.debug(
-          'Failed to connect to localhost, trying 127.0.0.1: {}'.format(
-              str(err)
-          )
+          'Failed to connect to localhost, trying 127.0.0.1: %s', err
       )
       self._conn = socket.create_connection(
           ('127.0.0.1', self.host_port), _SOCKET_CONNECTION_TIMEOUT
diff --git a/mobly/controllers/iperf_server.py b/mobly/controllers/iperf_server.py
index e99b298a..51101bdf 100644
--- a/mobly/controllers/iperf_server.py
+++ b/mobly/controllers/iperf_server.py
@@ -115,8 +115,8 @@ class IPerfServer:
 
   def __init__(self, port, log_path):
     self.port = port
-    self.log_path = os.path.join(log_path, 'iPerf{}'.format(self.port))
-    self.iperf_str = 'iperf3 -s -J -p {}'.format(port)
+    self.log_path = os.path.join(log_path, f'iPerf{self.port}')
+    self.iperf_str = f'iperf3 -s -J -p {port}'
     self.iperf_process = None
     self.log_files = []
     self.started = False
@@ -135,11 +135,9 @@ def start(self, extra_args='', tag=''):
     utils.create_dir(self.log_path)
     if tag:
       tag = tag + ','
-    out_file_name = 'IPerfServer,{},{}{}.log'.format(
-        self.port, tag, len(self.log_files)
-    )
+    out_file_name = f'IPerfServer,{self.port},{tag}{len(self.log_files)}.log'
     full_out_path = os.path.join(self.log_path, out_file_name)
-    cmd = '%s %s > %s' % (self.iperf_str, extra_args, full_out_path)
+    cmd = f'{self.iperf_str} {extra_args} > {full_out_path}'
     self.iperf_process = utils.start_standing_subprocess(cmd, shell=True)
     self.log_files.append(full_out_path)
     self.started = True
diff --git a/mobly/controllers/sniffer.py b/mobly/controllers/sniffer.py
index e1f3460b..3ae6311e 100644
--- a/mobly/controllers/sniffer.py
+++ b/mobly/controllers/sniffer.py
@@ -38,8 +38,8 @@ def create(configs):
     sniffer_subtype = c["SubType"]
     interface = c["Interface"]
     base_configs = c["BaseConfigs"]
-    module_name = "mobly.controllers.sniffer_lib.{}.{}".format(
-        sniffer_type, sniffer_subtype
+    module_name = (
+        f"mobly.controllers.sniffer_lib.{sniffer_type}.{sniffer_subtype}"
     )
     module = importlib.import_module(module_name)
     objs.append(
diff --git a/mobly/controllers/sniffer_lib/local/local_base.py b/mobly/controllers/sniffer_lib/local/local_base.py
index 0b2f6bf7..730aeecf 100644
--- a/mobly/controllers/sniffer_lib/local/local_base.py
+++ b/mobly/controllers/sniffer_lib/local/local_base.py
@@ -122,11 +122,11 @@ def start_capture(
           "Trying to start a sniff while another is still running!"
       )
     capture_dir = os.path.join(
-        self._logger.log_path, "Sniffer-{}".format(self._interface)
+        self._logger.log_path, f"Sniffer-{self._interface}"
     )
     os.makedirs(capture_dir, exist_ok=True)
     self._capture_file_path = os.path.join(
-        capture_dir, "capture_{}.pcap".format(logger.get_log_file_timestamp())
+        capture_dir, f"capture_{logger.get_log_file_timestamp()}.pcap"
     )
 
     self._pre_capture_config(override_configs)
diff --git a/mobly/controllers/sniffer_lib/local/tcpdump.py b/mobly/controllers/sniffer_lib/local/tcpdump.py
index 4f54cdb6..493438ab 100644
--- a/mobly/controllers/sniffer_lib/local/tcpdump.py
+++ b/mobly/controllers/sniffer_lib/local/tcpdump.py
@@ -26,7 +26,7 @@ def __init__(self, config_path, logger, base_configs=None):
 
     super().__init__(config_path, logger, base_configs=base_configs)
 
-    self._executable_path = shutil.which("tcpdump")
+    self._executable_path = shutil.which('tcpdump')
     if self._executable_path is None:
       raise sniffer.SnifferError(
           "Cannot find a path to the 'tcpdump' executable"
@@ -34,20 +34,18 @@ def __init__(self, config_path, logger, base_configs=None):
 
   def get_descriptor(self):
     """See base class documentation"""
-    return "local-tcpdump-{}".format(self._interface)
+    return f'local-tcpdump-{self._interface}'
 
   def get_subtype(self):
     """See base class documentation"""
-    return "tcpdump"
+    return 'tcpdump'
 
   def _get_command_line(
       self, additional_args=None, duration=None, packet_count=None
   ):
-    cmd = "{} -i {} -w {}".format(
-        self._executable_path, self._interface, self._temp_capture_file_path
-    )
+    cmd = f'{self._executable_path} -i {self._interface} -w {self._temp_capture_file_path}'
     if packet_count is not None:
-      cmd = "{} -c {}".format(cmd, packet_count)
+      cmd = f'{cmd} -c {packet_count}'
     if additional_args is not None:
-      cmd = "{} {}".format(cmd, additional_args)
+      cmd = f'{cmd} {additional_args}'
     return cmd
diff --git a/mobly/controllers/sniffer_lib/local/tshark.py b/mobly/controllers/sniffer_lib/local/tshark.py
index e48b1c6f..695a8b68 100644
--- a/mobly/controllers/sniffer_lib/local/tshark.py
+++ b/mobly/controllers/sniffer_lib/local/tshark.py
@@ -26,8 +26,8 @@ def __init__(self, config_path, logger, base_configs=None):
 
     super().__init__(config_path, logger, base_configs=base_configs)
 
-    self._executable_path = shutil.which("tshark") or shutil.which(
-        "/usr/local/bin/tshark"
+    self._executable_path = shutil.which('tshark') or shutil.which(
+        '/usr/local/bin/tshark'
     )
     if self._executable_path is None:
       raise sniffer.SnifferError(
@@ -37,22 +37,20 @@ def __init__(self, config_path, logger, base_configs=None):
 
   def get_descriptor(self):
     """See base class documentation"""
-    return "local-tshark-{}-ch{}".format(self._interface)
+    return f'local-tshark-{self._interface}'
 
   def get_subtype(self):
     """See base class documentation"""
-    return "tshark"
+    return 'tshark'
 
   def _get_command_line(
       self, additional_args=None, duration=None, packet_count=None
   ):
-    cmd = "{} -i {} -w {}".format(
-        self._executable_path, self._interface, self._temp_capture_file_path
-    )
+    cmd = f'{self._executable_path} -i {self._interface} -w {self._temp_capture_file_path}'
     if duration is not None:
-      cmd = "{} -a duration:{}".format(cmd, duration)
+      cmd = f'{cmd} -a duration:{duration}'
     if packet_count is not None:
-      cmd = "{} -c {}".format(cmd, packet_count)
+      cmd = f'{cmd} -c {packet_count}'
     if additional_args is not None:
-      cmd = "{} {}".format(cmd, additional_args)
+      cmd = f'{cmd} {additional_args}'
     return cmd
diff --git a/mobly/logger.py b/mobly/logger.py
index 1d85d35b..ff6b19c3 100644
--- a/mobly/logger.py
+++ b/mobly/logger.py
@@ -117,9 +117,7 @@ def epoch_to_log_line_timestamp(epoch_time, time_zone=None):
 
   Args:
     epoch_time: integer, an epoch timestamp in ms.
-    time_zone: instance of tzinfo, time zone information.
-      Using pytz rather than python 3.2 time_zone implementation for
-      python 2 compatibility reasons.
+    time_zone: instance of datetime.tzinfo, time zone information.
 
   Returns:
     A string that is the corresponding timestamp in log line timestamp
diff --git a/mobly/utils.py b/mobly/utils.py
index 2defb698..e0df8cf1 100644
--- a/mobly/utils.py
+++ b/mobly/utils.py
@@ -397,7 +397,8 @@ def run_command(
     timeout=...,
     cwd=...,
     env=...,
-    universal_newlines: Literal[False] = ...,
+    text: Literal[False] = ...,
+    universal_newlines: Literal[False] | None = ...,
 ) -> tuple[int, bytes, bytes]:
   ...
 
@@ -411,7 +412,8 @@ def run_command(
     timeout=...,
     cwd=...,
     env=...,
-    universal_newlines: Literal[True] = ...,
+    text: Literal[True] = ...,
+    universal_newlines: Literal[True] | None = ...,
 ) -> tuple[int, str, str]:
   ...
 
@@ -424,7 +426,8 @@ def run_command(
     timeout=None,
     cwd=None,
     env=None,
-    universal_newlines=False,
+    text=False,
+    universal_newlines=None,
 ):
   """Runs a command in a subprocess.
 
@@ -452,8 +455,9 @@ def run_command(
     env: dict, a mapping that defines the environment variables for the
       new process. Default behavior is inheriting the current process'
       environment.
-    universal_newlines: bool, True to open file objects in text mode, False in
+    text: bool, True to open file objects in text mode, False in
       binary mode.
+    universal_newlines: bool, legacy alias for `text`.
 
   Returns:
     A 3-tuple of the consisting of the return code, the std output, and the
@@ -462,6 +466,8 @@ def run_command(
   Raises:
     subprocess.TimeoutExpired: The command timed out.
   """
+  if universal_newlines is not None:
+    text = universal_newlines
   if stdout is None:
     stdout = subprocess.PIPE
   if stderr is None:
@@ -473,7 +479,7 @@ def run_command(
       shell=shell,
       cwd=cwd,
       env=env,
-      text=universal_newlines,  # "text" is introdcued in Python 3.7.
+      text=text,
   )
   out, err = None, None
   try:
diff --git a/pyproject.toml b/pyproject.toml
index deb56698..476302f9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -21,7 +21,7 @@ Homepage = "https://github.com/google/mobly"
 Download = "https://github.com/google/mobly/tarball/1.13.1"
 
 [project.optional-dependencies]
-testing = [ "mock", "pytest", "pytz",]
+testing = [ "pytest",]
 
 [tool.setuptools]
 include-package-data = false
diff --git a/tests/mobly/base_test_test.py b/tests/mobly/base_test_test.py
index d74ed054..92916d83 100755
--- a/tests/mobly/base_test_test.py
+++ b/tests/mobly/base_test_test.py
@@ -3060,7 +3060,9 @@ class RecoverableError(Exception):
       except RecoverableError:
         pass
 
-    logging_patch.debug.assert_called_with('[TestClass]#stage <<< END <<<')
+    logging_patch.debug.assert_called_with(
+        base_test.TEST_STAGE_END_LOG_TEMPLATE, 'TestClass', 'stage'
+    )
 
 
 if __name__ == '__main__':
diff --git a/tests/mobly/controllers/android_device_lib/apk_utils_test.py b/tests/mobly/controllers/android_device_lib/apk_utils_test.py
index 36f2ed2b..5698274d 100644
--- a/tests/mobly/controllers/android_device_lib/apk_utils_test.py
+++ b/tests/mobly/controllers/android_device_lib/apk_utils_test.py
@@ -27,7 +27,7 @@
 class ApkUtilsTest(unittest.TestCase):
 
   def setUp(self):
-    super(ApkUtilsTest, self).setUp()
+    super().setUp()
     self.mock_device = mock.MagicMock()
     self.mock_device.adb.current_user_id = 0
 
diff --git a/tests/mobly/logger_test.py b/tests/mobly/logger_test.py
index d975ac79..e10bca93 100755
--- a/tests/mobly/logger_test.py
+++ b/tests/mobly/logger_test.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import datetime
 import logging
 import os
 import shutil
@@ -20,7 +21,6 @@
 from unittest import mock
 
 from mobly import logger
-import pytz
 
 
 class LoggerTest(unittest.TestCase):
@@ -34,7 +34,7 @@ def tearDown(self):
 
   def test_epoch_to_log_line_timestamp(self):
     actual_stamp = logger.epoch_to_log_line_timestamp(
-        1469134262116, time_zone=pytz.utc
+        1469134262116, time_zone=datetime.timezone.utc
     )
     self.assertEqual('07-21 20:51:02.116', actual_stamp)
 
diff --git a/tests/mobly/utils_test.py b/tests/mobly/utils_test.py
index 84f5afd6..2c29dfcf 100755
--- a/tests/mobly/utils_test.py
+++ b/tests/mobly/utils_test.py
@@ -22,7 +22,6 @@
 import signal
 import socket
 import subprocess
-import sys
 import tempfile
 import threading
 import time
@@ -364,6 +363,16 @@ def test_run_command_with_universal_newlines_true(self):
 
     self.assertIsInstance(out, str)
 
+  def test_run_command_with_text_false(self):
+    _, out, _ = utils.run_command(self.sleep_cmd(0.01), text=False)
+
+    self.assertIsInstance(out, bytes)
+
+  def test_run_command_with_text_true(self):
+    _, out, _ = utils.run_command(self.sleep_cmd(0.01), text=True)
+
+    self.assertIsInstance(out, str)
+
   def test_start_standing_subproc(self):
     try:
       p = utils.start_standing_subprocess(self.sleep_cmd(4))
@@ -487,10 +496,6 @@ def test_stop_standing_subproc_and_descendants(self):
     subprocess_a.join(timeout=1)
     mock_subprocess_a_popen.wait.assert_called_once()
 
-  @unittest.skipIf(
-      sys.version_info >= (3, 4) and sys.version_info < (3, 5),
-      'Python 3.4 does not support `None` max_workers.',
-  )
   def test_concurrent_exec_when_none_workers(self):
     def adder(a, b):
       return a + b
diff --git a/tox.ini b/tox.ini
index 402351a9..4be967ae 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,7 +4,6 @@ envlist = py3
 [testenv]
 deps =
     pytest
-    pytz
 commands =
     pytest