Log Message:
py-mercurial: update to 6.7.3.

= Mercurial 6.7.3 =

 * setup: display return code information about failed `hg` call
 * bundle-spec: properly identify changegroup-less bundle
 * bundle-spec: properly parse boolean configuration as boolean
 * matchers: fix the bug in rust PatternMatcher that made it cut off early
 * match: fix the "visitdir" method on "rootfilesin" matchers
 * match: fix the rust-side bug in visit_children_set for rootfilesin matchers
 * match: strengthen visit_children_set invariant, Recursive means "all \ 
files"
 * wireprotoserver: ensure that output stream gets flushed on exception
 * re2: make errors quiet
 * dirstate-v2: add check of parent/child nodes being related when writing
 * dirstate-v2: check that root nodes are at the root before writing
 * rust-cpython: don't swallow the dirstate error message
 * rust: blanket implementation of Graph for Graph references
 * Various fixes to `admin::verify`