docs: Document usage of python -m pip if pip is not working

[Makman2]

On windows sometimes pip is screwed, we maybe should document the usage of python -m pip then.

Though I'm not sure, it's in fact a platform problem^^

[gitmate-bot]

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CC @sils1297, @AbdealiJK

[jschwarzwalder]

On a Windows 8 a machine, trying to get coala up and running user found these instructions:
http://coala-analyzer.org/#details

sudo pip3 install coala-bears does not work, pip3 install coala-bears does not work, pip install coala-bears does not work.

We tried to add C:\Python34\Scripts to the path, and reinstalling Python 3.5 and continued to get the error message

Fatal error in launcher: Unable to create process using '"C:\Python34\python.exe" "C:\Python34\Scripts\pip3.exe" -V'
when we tried to run pip3 -V I got the message
pip 8.1.2 from c:\python27\lib\site-packages (python 2.7)
another solution we tried was to delete pip3.exe from the C:\Python27 folder

[AbdealiLoKo]

Could you provide more details about how python was installed?
It seems to me as though python2, python3, pip2 and pip3 are getting confused by the system.

So:
Which versions of python are installed? Are these installed from the python exe at python.org ?
What's in the path (related to python) ?

I think:
"C:\Python34\python.exe" -m pip install coala-bears
Should work for you

[jschwarzwalder]

I have Python27 and Python34 installed on my computer
I had someone who did this for me on Monday using this tutorial from DjangoGirls
It is possible they downloaded from an alternative source

I had to add those folders to my path
Before today I only have Python27/Scripts in my path

As part of my troubleshooting I tried to add Python34/Scripts to my path and even removed Python27/Scripts from my path
each time I was getting the same error that Fatal error in launcher: Unable to create process using '"C:\Python34\python.exe"

[jschwarzwalder]

I downloaded Python 3.5.1 and reinstalled it from https://www.python.org/downloads/ to try and solve the problem but continued to get the issue.

[jschwarzwalder]

We were able to use python3 -m pip install coala-bears and found success

[Adrianzatreanu]

This issue was moved to coala/documentation#37