Hello. streamlink uses mock at least once: https://github.com/streamlink/streamlink/blob/0.2.0/tests/test_cmdline.py#L9 Please fix.
Only 0.1.0 is affected now.
Fixed in new version https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=3d599eb34b8863664dcf6b02ffe6da7b681e3a31 and live version https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=d377f979b7ff6cbb1185dc02b18b4770eff56a3f