Fix setup.py to install dependencies.

[sydp]

Fixes #619

[sydp]

When running python setup.py install, I get the following error:

File "/tmp/easy_install-ntcdk5x3/cryptography-36.0.1/setup.py", line 14, in <module>
    from distutils.command.bdist_msi import bdist_msi
ModuleNotFoundError: No module named 'setuptools_rust'

Seems to be a known issue when installing cryptography as a dependency (pyca/cryptography#6411)

Manually installing setuptools_rust via pip resolves this issue.

[joachimmetz]

@sydp thx for the suggested changes, but I'll address this differently by changing parse_requirements_from_file to return a list. This needs to be changed in l2tdevtools as well since it generates setup.py.

[sydp]

Sounds good. Thanks.