Fixes to get for python3 virtualenvs working

[jeethu]

I've been happily using powerline-shell on OSX for quite some time now. Thanks for building it.

I created a Python 3.4 virtualenv using Python3's builtin pyvenv command and powerline-shell would break anytime I activate it, powerline-shell would barf out. I decided to spend some time making things cross compatible between python2 (>= 2.6) and python3. It turned out to be far easier than I'd anticipated it to be.

I've been using this patched version for the past couple of days with Python 2.7 and Python 3.4. I found that this issue had been reported earlier on #118, but I couldn't find a way to attach a pull request against that issue. I've also got another branch with a few pep8 fixes on top of this, but that should probably be addressed separately.

[benklaasen]

Hi - I'm on the latest powerline-shell on Xubuntu 15.10. Invoking bin/activate in a virtualenv created with pyvenv from the 15.10 repo still effectively hangs my shell. Here's the output of source bin/activate after running set -x:

+ source bin/activate
++ deactivate nondestructive
++ '[' -n '' ']'
++ '[' -n '' ']'
++ '[' -n /bin/bash -o -n '' ']'
++ hash -r
++ '[' -n '' ']'
++ unset VIRTUAL_ENV
++ '[' '!' nondestructive = nondestructive ']'
++ VIRTUAL_ENV=/home/ben/bin/Jupyter
++ export VIRTUAL_ENV
++ _OLD_VIRTUAL_PATH=/home/ben/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/home/ben/bin:/home/ben/.local/bin/:.
++ PATH=/home/ben/bin/Jupyter/bin:/home/ben/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/home/ben/bin:/home/ben/.local/bin/:.
++ export PATH
++ '[' -n '' ']'
++ '[' -z '' ']'
++ _OLD_VIRTUAL_PS1='\[\e[38;5;250m\]\[\e[48;5;240m\] \u \[\e[48;5;238m\]\[\e[38;5;240m\]\[\e[38;5;250m\]\[\e[48;5;238m\] \h \[\e[48;5;31m\]\[\e[38;5;238m\]\[\e[38;5;15m\]\[\e[48;5;31m\] ~ \[\e[48;5;237m\]\[\e[38;5;31m\]\[\e[38;5;250m\]\[\e[48;5;237m\] bin \[\e[48;5;237m\]\[\e[38;5;244m\]\[\e[38;5;250m\]\[\e[48;5;237m\] Jupyter \[\e[48;5;236m\]\[\e[38;5;237m\]\[\e[38;5;15m\]\[\e[48;5;236m\] \$ \[\e[0m\]\[\e[38;5;236m\]\[\e[0m\] '
++ '[' 'x(Jupyter) ' '!=' x ']'
++ PS1='(Jupyter) \[\e[38;5;250m\]\[\e[48;5;240m\] \u \[\e[48;5;238m\]\[\e[38;5;240m\]\[\e[38;5;250m\]\[\e[48;5;238m\] \h \[\e[48;5;31m\]\[\e[38;5;238m\]\[\e[38;5;15m\]\[\e[48;5;31m\] ~ \[\e[48;5;237m\]\[\e[38;5;31m\]\[\e[38;5;250m\]\[\e[48;5;237m\] bin \[\e[48;5;237m\]\[\e[38;5;244m\]\[\e[38;5;250m\]\[\e[48;5;237m\] Jupyter \[\e[48;5;236m\]\[\e[38;5;237m\]\[\e[38;5;15m\]\[\e[48;5;236m\] \$ \[\e[0m\]\[\e[38;5;236m\]\[\e[0m\] '
++ export PS1
++ '[' -n /bin/bash -o -n '' ']'
++ hash -r
++ _update_ps1
+++ /home/ben/bin/powerline-shell/powerline-shell.py 0
++ PS1=

Let me know if you need more information.

This isn't specific to pyvenv; the same thing happens using virtualenv to set up a Python 3 virtual environment:

$ virtualenv -p $(which python3) .
Already using interpreter /usr/bin/python3
Using base prefix '/usr'
New python executable in ./bin/python3
Also creating executable in ./bin/python
Installing setuptools, pip...done.
$ source bin/activate

[benklaasen]

Just to correct an earlier mistaken claim: my shell is responsive, there's just no prompt. Line editing works fine.

[benklaasen]

OK, I was being a dope; I'd failed to run install.py after doing a git pull.