Check for write access for bashcompletion via os.access
Check for write access for bashcompletion via os.access

Alternative version of pull request rockymeza/wifi#41 (which apparently
isn't worked on any more) which checks for write access before
attempting to install the bashcompletion addition during
installation -- if only installed in a library into a virtualenv
the installation will now complete without an issue.

cangelis/wifi,foosel/wifi,foosel/wifi,rockymeza/wifi,simudream/wifi,cangelis/wifi,rockymeza/wifi,nicupavel/wifi,simudream/wifi,nicupavel/wifi