Feature Request: raise a more informative message when geos_c.dll isn't found

[kandersolar]

Installing shapely from pip instead of conda is a frequent roadblock for users that haven't been exposed to binary python dependencies:

• Could not find module #106
• https://groups.google.com/g/pvlib-python/c/0WM8Soc8PiQ
• https://stackoverflow.com/questions/65790878/error-winerror-126-the-specified-module-could-not-be-found
• https://stackoverflow.com/questions/64671004/could-not-find-module-pvfactors
• https://stackoverflow.com/questions/64037211/oserror-winerror-126-the-specified-module-could-not-be-found-using-pvfactor

I see in #106 that the shapely dependency is planned to be dropped in the future -- will that be happening in the near future? If it might be a while, what do you think about wrapping shapely imports in a try/except and raising a new error with a helpful hint about installing shapely from conda instead of pip? If that sounds like a good idea, I'm happy to open a PR -- it might be as simple as just adding something like this at the top of __init__.py, or it might need it everywhere shapely is imported, not sure:

try:
    import shapely
except OSError:
    # can't use "raise from" here because py2.7 doesn't support it.  Or drop 2.7 support, see #107
    raise ImportError("Something helpful about conda vs pip for shapely") 

[anomam]

@kanderso-nrel thanks so much for your message and for tracking all these user issues, I had no idea it was such a big problem for people. Unfortunately I don't have any time to work on dropping the shapely dependency, but I do very much welcome any contributions that can make things easier for users. So please feel free to open a PR and I will happily review it!

Something in the top __init__.py file would be good enough for me.