setup: raise minimum Python version to 2.7.4 On older Python versions, Mercurial is not really usable because of https://bugs.python.org/issue10211. Recently someone reported a crash on the mailing list when running Mercurial on Python 2.7.3. There was consensus that fixing compatibility for a Python version more than 7 years old is not worth it. So, instead of making Mercurial crash with an obscure exception, this patch raises the minimum Python version to 2.7.4.