packaging: follow hg's supported python version (>= 2.7) "Mercurial 4.3 and newer require Python 2.7." (From https://www.mercurial-scm.org/wiki/SupportedPythonVersions) Also add X- prefix, because that's the correct form, apparently. This line can also be removed in future, since "When Debian supported multiple Python versions, X-Python-Version was used, but it is obsolete now as no supported Debian release supports anything other than python2.7." (From https://wiki.debian.org/Python/LibraryStyleGuide) That page also mentions "X-Python3-Version".

--- a/debian/control	Thu Jun 13 13:19:44 2019 +0800
+++ b/debian/control	Thu Jun 13 13:27:26 2019 +0800
@@ -14,7 +14,7 @@
  imagemagick,
  librsvg2-bin,
  wget,
-Python-Version: >= 2.6
+X-Python-Version: >= 2.7
 Homepage: https://www.mercurial-scm.org/doc/evolution/
 
 Package: mercurial-evolve