tests/test-config-case.t

hghave: wrap command in 'sh -c "..."' for has_pyflakes()

Without this, the has_pyflakes() check always fails in MSYS on Windows.

  $ echo '[Section]' >> $HGRCPATH
  $ echo 'KeY = Case Sensitive' >> $HGRCPATH
  $ echo 'key = lower case' >> $HGRCPATH

  $ hg showconfig Section
  Section.KeY=Case Sensitive
  Section.key=lower case