Message10514

I have experienced this issue, these are my 2 cents:

IMHO, the error is triggered by two conditions:
 1. sys.platform returns "javaM.m.p_u". (that's the same than jython 2.5.2, so it might be ok)
 2. Something (probably `import pip`) when pip.exe is run creates a %TEMP%\pip_build_<username> folder, that raises an `OSError` in the `os.mkdir` because that temporary directory already exists.

To be able to solve this problem, we need to answer 2 questions:
 1. This is an issue with pip "1.6dev", are we still using that version? Message 10397, indicates that we are using a newer pip.
 2. If so, will this issue be fixed by preventing the temp folder for being created if pip is already installed, or by fixing the path the code takes take the True branch of the `if sys.platform == 'win32':` conditional.