"Successfully installed pip x.y.z" message can print an incorrect version

[tdsmith]

In step 4, pip will print "Successfully installed pip 1.5.6" even though 6.1.0 has been correctly installed.

To reproduce:

1. mkdir test; cd test; virtualenv .; . bin/activate

2. Query pip's version:

   (test)darkside:test tim$ pip -V
   pip 1.5.6 from /Users/tim/test/lib/python2.7/site-packages (python 2.7)
   

   Pip is a flat installation:

   (test)darkside:test tim$ python -c "import pip; print pip.__file__"
   /Users/tim/test/lib/python2.7/site-packages/pip/__init__.pyc
   

3. Install a newer but not newest pip egg: easy_install pip==6.0.8

   (test)darkside:test tim$ pip -V
   pip 6.0.8 from /Users/tim/test/lib/python2.7/site-packages/pip-6.0.8-py2.7.egg (python 2.7)
   

4. Upgrade pip: pip install -U pip

   (test)darkside:test tim$ pip install -U pip
   You are using pip version 6.0.8, however version 6.1.0 is available.
   You should consider upgrading via the 'pip install --upgrade pip' command.
   Collecting pip from https://pypi.python.org/packages/py2.py3/p/pip/pip-6.1.0-py2.py3-none-any.whl#md5=94faa2660c3a2ebe7d015d62c8726259
   Using cached pip-6.1.0-py2.py3-none-any.whl
   Installing collected packages: pip
   Found existing installation: pip 6.0.8
     Uninstalling pip-6.0.8:
       Successfully uninstalled pip-6.0.8
   
   Successfully installed pip-1.5.6
   (test)darkside:test tim$ pip -V
   pip 6.1.0 from /Users/tim/test/lib/python2.7/site-packages (python 2.7)
   

5. Upgrade pip again: pip install -U pip

   (test)darkside:test tim$ pip install -U pip
   Collecting pip
   Using cached pip-6.1.0-py2.py3-none-any.whl
   Installing collected packages: pip
   Found existing installation: pip 1.5.6
     Uninstalling pip-1.5.6:
       Successfully uninstalled pip-1.5.6
   Successfully installed pip-6.1.0
   

System configuration:
Python 2.7.9 (Homebrew)
OS X 10.10.2

[ionelmc]

I've seen this issue too, cause seems to be pip leaving multiple .dist-info dirs around for the same package.

[xavfernandez]

Hopefully it was fixed in #3723.
If you're still facing the issue in pip 9.0.1, please re-open an issue with reproduction steps.