hgfixes: add a fixer to convert plain strings to bytestrings This patch implements a 2to3 fixer that converts all plain strings in a python source file to byte strings syntax. Example: foo = 'Normal string' would become foo = b'Normal string' The motivation behind this fixer can be found in http://selenic.com/pipermail/mercurial-devel/2010-June/022363.html or, in other words: the current hg source assumes that _most_ strings are "meant" to be byte sequences, so it makes sense to make the convertion implemented by this patch. As mentioned above, not all mercurial modules want to use strings as bytes, examples include i18n (which uses unicode), and demandimport (in py3k, module names are normal strings, thus unicode, and there's no need for a convertion). Therefore, these modules are blacklisted in the fixer. There are also a few functions that can take only unicode arguments, thus the convertion shouldn't be done for those.