Previously, the check script would detect breezy as part of the stdlib if
installed using the debian package manager.
This silence the following complains:
tests/test-convert-bzr.t:117: imports not lexically sorted: breezy.bzr.bzrdir < sys
tests/test-convert-bzr.t:117: stdlib import "breezy.bzr.bzrdir" follows local import: breezy
tests/test-convert-bzr-ghosts.t:7: imports not lexically sorted: breezy.bzr.bzrdir < sys
tests/test-convert-bzr-ghosts.t:7: stdlib import "breezy.bzr.bzrdir" follows local import: breezy
tests/test-convert-bzr-treeroot.t:7: imports not lexically sorted: breezy.bzr.bzrdir < sys
tests/test-convert-bzr-treeroot.t:7: stdlib import "breezy.bzr.bzrdir" follows local import: breezy