Bug#697402: bzr-gtk: causes crash in pydoc -k when python-gtk2 is also installed

[Matthew Woodcraft <matthew@woodcraft.me.uk>]

Debian has in the past contained Python packages which have side-effects
when imported which are worse than just crashing the calling process
(for example, I've had pydoc crash my window manager).

Arguably all such cases are bugs in those packages, but it seems likely
that such bugs will appear again. And of course the user might have
local Python packages which do dangerous things when imported.

So I think pydoc is just wrong to believe it can safely call
pkgutil.walk_packages() with no explicit path.

(This behaviour can be particularly entertaining when combined with
zsh's tab-completion for 'python -m', which currently calls pydoc in a
similar way [#691638].)

-M-