Log Message:
py-mercurial: update to 6.4.1.

= Mercurial 6.4.1 =

 * rhg: fix a bug in path encoding
 * rhg: don't crash on empty directory names in path_encode, just in case
 * commands: correct documentation of hg serve’s --ipv6 options
 * run-tests: remove obsolete coverage check and packaging import (issue6805)
 * chg: populate CHGHG if not set
 * match: sort patterns before compiling them into a regex
 * match: match explicit file using a set
 * rebase: do not cleanup the working copy when --dry-run is used (issue6802)
 * sslutil: set context security level for legacy tls testing (issue6760)