convert/svn: abort operation when python bindings are not available
Subversion python bindings check was not present in svn_sink source
class which made it fail while using svn as destination repository.
Added a more maintainble svn bindings check for svn_source and svn_sink
classes.
Mercurial's documentation is kept in reStructuredText format, which is
a simple plain text format that's easy to read and edit:
http://docutils.sourceforge.net/rst.html
It's also convertible to a variety of other formats including standard
UNIX man page format and HTML. You'll need to install Docutils:
http://docutils.sourceforge.net/
Use the Makefile in this directory to generate the man and HTML pages.