let run-tests run optional code coverage tests.
to enable, set env var TEST_COVERAGE to non-empty string. run-tests will
print report after running.
after coverage run, file tests/.coverage will contain coverage data. use
tests/coverage.py to get more info, like annotated source code.
adding foo
adding bar
adding baz/bletch
test-archive-TIP/bar
test-archive-TIP/baz/bletch
test-archive-TIP/foo
test-archive-TIP/bar
test-archive-TIP/baz/bletch
test-archive-TIP/foo
Archive: archive.zip
testing: test-archive-TIP/bar OK
testing: test-archive-TIP/baz/bletch OK
testing: test-archive-TIP/foo OK
No errors detected in compressed data of archive.zip.