Python 2.7 & MinGW32
In the event that you will be installing unfamiliar Python modules, take some time to do the research to understand what kind of package it really is. For instance, psycopg2, a PostgreSQL adapter, is a C extension module, so you will need your system to have a capable C compiler.
I am about to transfer content from a MongoDB database to PostgreSQL on Heroku. Now of course there is already a Mongo add-on, but it requires giving credit card information for a free trial whereas the PostgreSQL does not. As usual, I didn't bother to do any prep research and went ahead and ran 'pip install psycopg2' which lead to some exciting errors. The first being: error: Setup script exited with error: Unable to find vcvarsall.bat
Now, I had definitely seen this one before, but thought I had already fixed it by adding
[build]
compiler=mingw32
to the distutils.cfg file from C:\Python27\distutils. However I had overlooked the simple fact that I had another config file to edit in the same way: the distutils.cfg located in my project's virtualenv. You can find it in the env's Lib\distutils.
And that was that! ...just kidding! Time for error number two to make an unwanted appearance.
cc1.exe: error: unrecognized command line option '-mno-cygwin'
error: Setup script exited with error: command 'gcc' failed with exit status 1
Hmm. That's a weird one. I was pretty confused regarding the source of this error. So, I took to the internet and luckily was not alone in my confusion. Apparently more current versions of GCC (GNU Compiler Collection) don't have the option '-mno-cygwin' which specifies that the MinGW internal interface is to be used instead of Cygwin's and thereby any code using the option is deprecated. Guess where we can find this useless option? In our good friend Python's cygwincompiler.py file back in the directory we started from: C:\Python27\distutils. Luckily, this is another simple fix. Remove all instances of '-mno-cygwin' and the build should successfully access MinGW.
