Fix windows test errors

[cansarigol]

https://github.com/cansarigol/pdbr/runs/5351140347?check_suite_focus=true

____________________ ERROR collecting tests/test_magic.py _____________________
ImportError while importing test module 'D:\a\pdbr\pdbr\tests\test_magic.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
c:\hostedtoolcache\windows\python\3.7.9\x64\lib\importlib\__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests\test_magic.py:7: in <module>
    import pexpect
E   ModuleNotFoundError: No module named 'pexpect'

[Shivam-Shrivastav]

This stackoverflow issue https://stackoverflow.com/questions/22669686/importerror-no-module-named-pexpect might help

[cansarigol]

@Shivam-Shrivastav thanks