Add proper shebangs to all Python scripts

[mgorny]

Currently, some of the scripts don't have a shebang at all, some others have it pointing towards /usr/local/bin/python. With this patch, all shebangs use /usr/bin/env python consistently.

[wiredfool]

The current situation is certainly suboptimal.

There's been previous discussion of this in issue #167. This should work on the builtin pythons for linux, I'm unclear on the effects in a virtualenv, especially if pillow has been installed for the system python but not in the virutalenv. I'm also concerned about the effect on windows. @cgohlke: Can you comment on that?

[mgorny]

Well, I'm not really into virtualenv but I think it should work properly. At least I didn't hear of anything failing because of it, and I guess it's common enough shebang to have been well-tested.

As for Windows, I don't know of any thing that would fail. Considering that Windows either doesn't use shebangs (native) or uses a virtual env like MinGW or Cygwin, it should all work fine.

[wiredfool]

The thing that concerns me with virtual env is that /usr/bin/env python will be from within the virtual env, but the scripts will be from the system python (or system python3) installation. I'm pretty sure that running the scripts will fail in that case.

Also, is /usr/bin/env python going to work at all if we've only been installed under python3?

[mgorny]

Firstly, I'd like to note that distutils changes shebangs when it installs scripts. Therefore, the scripts which I env python here, end up being installed with full path to the Python interpreter:

$ head -1 /tmp/z/usr/bin/pilfont.py
#!/usr/bin/python2.7

However, if the script has no shebang, it will be installed with no shebang at all. That's the main reason I'd like them all to have valid shebang

[wiredfool]

Oh, if distutils rewrites them, then I'm a lot happier with whatever we put in there.

[wiredfool]

Looks like it works with virtualenv, If debian and fedora have issues with it, we can deal with it in the packaging. (at least for debian.)