Fix for #373

[pradyunsg]

I hope to resolve #373 in this PR.

[pradyunsg]

@NiklasRosenstein Thanks for checking!

Could you provide a set of steps to reproduce the issue? I'd like to add a test for this behaviour to ensure it doesn't break again in the future.

[NiklasRosenstein]

I've tried to reproduce the issue on Ubuntu 16.04 on Python 3.5.2 and Pip 9.0.1, but wasn't able to. I can only reproduce it on Windows 10 using the same Python and Pip versions. Again, using this command

$ pip install --prefix nodepy_modules/.pip 'appdirs>=1.4.2' 'click>=6.7' 'distlib>=0.2.4' 'hammock>=0.2.4' 'jsonschema>=2.6.0' 'requests>=2.13.0' --ignore- installed
Collecting appdirs>=1.4.2
  Using cached appdirs-1.4.3-py2.py3-none-any.whl
Collecting click>=6.7
  Using cached click-6.7-py2.py3-none-any.whl
Collecting distlib>=0.2.4
  Using cached distlib-0.2.5.zip
Collecting hammock>=0.2.4
Collecting jsonschema>=2.6.0
  Using cached jsonschema-2.6.0-py2.py3-none-any.whl
Collecting requests>=2.13.0
  Using cached requests-2.14.2-py2.py3-none-any.whl
Installing collected packages: appdirs, click, distlib, requests, hammock, jsonschema
  Running setup.py install for distlib ... done
Exception:
Traceback (most recent call last):
  File "c:\users\niklas\repos\pip\pip\basecommand.py", line 215, in main
    status = self.run(options, args)
  File "c:\users\niklas\repos\pip\pip\commands\install.py", line 342, in run
    prefix=options.prefix_path,
  File "c:\users\niklas\repos\pip\pip\req\req_set.py", line 784, in install
    **kwargs
  File "c:\users\niklas\repos\pip\pip\req\req_install.py", line 922, in install
    with open(inst_files_path, 'w') as f:
FileNotFoundError: [Errno 2] No such file or directory: 'nodepy_modules\\.pip\\Lib\\site-packages\\distlib-0.2.5-py3.5.egg-info\\installed-files.txt'

The installation succeeds after upgrading to Pip with your patch.

niklas@DESKTOP-RQTQ13S  ~/Desktop
$ rm -r nodepy_modules/

niklas@DESKTOP-RQTQ13S  ~/Desktop
$ pip --version
pip 10.0.0.dev0 from c:\users\niklas\repos\pip (python 3.5)

niklas@DESKTOP-RQTQ13S  ~/Desktop
$ pip install --prefix nodepy_modules/.pip 'appdirs>=1.4.2' 'click>=6.7' 'distlib>=0.2.4' 'hammock>=0.2.4' 'jsonschema>=2.6.0' 'requests>=2.13.0' --ignore- installed
Collecting appdirs>=1.4.2
  Using cached appdirs-1.4.3-py2.py3-none-any.whl
Collecting click>=6.7
  Using cached click-6.7-py2.py3-none-any.whl
Collecting distlib>=0.2.4
  Using cached distlib-0.2.5.zip
Collecting hammock>=0.2.4
Collecting jsonschema>=2.6.0
  Using cached jsonschema-2.6.0-py2.py3-none-any.whl
Collecting requests>=2.13.0
  Using cached requests-2.14.2-py2.py3-none-any.whl
Installing collected packages: appdirs, click, distlib, requests, hammock, jsonschema
  Running setup.py install for distlib ... done
Successfully installed appdirs-1.4.3 click-6.7 distlib-0.2.5 hammock-0.2.4 jsonschema-2.6.0 requests-2.14.2

[pradyunsg]

Awesome! Thanks a lot!

I don't have a Windows 10 machine handy. :/

I'll add a test based on what you describe. I'm hoping I can have it breaking on master and passing on this branch. I guess I'll use AppVeyor.

[pradyunsg]

@dstufft Can this be merged without a test?