tests: adapt now that Mercurial clears the merge state for empty wdir `hg evolve` forgot to clear the merge state when its attempt to commit resulted in no commit because the working copy had no changes. That resulted in test-evolve-issue5967.t showing a conflict state that shouldn't be there. The responsibility for clearing the merge state was moved into Mercurial in Mercurial in 6a34e438461b (commit: clear resolved mergestate even if working copy is clean, 2020-02-28), so the bug is now fixed in `hg evolve`, which impacts that test case. CORE-TEST-OUTPUT-UPDATE: 6a34e438461b

#require test-repo

  $ checkflake8() {
  >   if ! (which flake8 > /dev/null); then
  >     echo skipped: missing tool: flake8;
  >     exit 80;
  >   fi;
  > };
  $ checkflake8

Copied from Mercurial core (60ee2593a270)

  $ cd "`dirname "$TESTDIR"`"

run flake8 if it exists; if it doesn't, then just skip

  $ hg files -0 'set:(**.py or grep("^#!.*python")) - removed()' \
  > -X hgext3rd/evolve/thirdparty \
  > 2>/dev/null \
  > | xargs -0 flake8