Cannot import petab.v2 without scipy installed

[sebapersson]

Without scipy installed on version 0.8.2, the following error occurs when running:

import petab.v2

Stacktrace:

Traceback (most recent call last):
  File "<python-input-4>", line 1, in <module>
    import petab.v2
  File ".../petab/v2/__init__.py", line 7, in <module>
    from petab.v1.distributions import *  # noqa: F401, E402
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../petab/v1/distributions.py", line 18, in <module>
    from scipy.stats import (
    ...<8 lines>...
    )
ModuleNotFoundError: No module named 'scipy'

I am not a Python expert, but I guess scipy should either be listed as a required dependency, or the import should be made lazy so it is only needed when the relevant functionality is used.