Require networkx>=2.4 due to Python 3.9. (#109)

Author: tobiasraabe

docs/changes.rst

@@ -32,6 +32,8 @@ all releases are available on `PyPI <https://pypi.org/project/pytask>`_ and
 - :gh:`107` adds and new hook ``pytask_unconfigure`` which makes pytask return
   :func:`pdb.set_trace` at the end of a session which allows to use ``breakpoint()``
   inside test functions using pytask.
+- :gh:`109` makes pytask require networkx>=2.4 since previous versions fail with Python
+  3.9.
 
 
 0.0.14 - 2021-03-23

setup.cfg

@@ -37,7 +37,7 @@ install_requires =
     attrs>=17.4.0
     click
     click-default-group
-    networkx
+    networkx>=2.4
     pluggy
     pony>=0.7.13
     rich

tox.ini

@@ -21,7 +21,7 @@ conda_deps =
     attrs
     click
     click-default-group
-    networkx
+    networkx>=2.4
     pluggy
     pony >= 0.7.13
     rich