install_binary_dist doesn't respect directory permissions

[vrachnis]

It appears that the install_binary_dist function tries to create a missing subdirectory even if it doesn't have the permissions to do so.
More specifically, the issue appears while trying to install the greenlet package, which is supposed to install a header file in the include directory of the virtualenv. However pip-accel tries to create the directory $VIRTUAL_ENV/include/python2.7/greenlet which is problematic since $VIRTUAL_ENV/include/python2.7 is a symbolic link to /usr/local/include/python2.7 which is owned by root.
Pip works around this issue by installing the header file in $VIRTUAL_ENV/include/site/python2.7/.

Currently, since the installation procedure is interrupted, the virtual environment is left in a "semi-broken" state because greenlet is not really installed, but the egg-info is in place making pip think that greenlet is installed. Of course, running pip uninstall greenlet && pip install greenlet fixes the environment.

[xolox]

Thanks for the clear bug report and suggested fix! I never knew Python package distributions could include C header files (although of course it makes sense in hindsight); I'm learning more and more about Python packaging as pip-accel matures :-). I just published pip-accel 0.9.7 to GitHub and PyPI. This new release should fix the bug you reported. Can you confirm?

[vrachnis]

Indeed, now the directory structure is the same that pip creates. Thanks for the quick resolution :)