[test] Avoid ambiguous variable name "l" in unittest_req.py This is an error (E741) from flake8 3.5.

[tox] Bound flake8 version to >=3.4, <3.5 The code base is not clean with 3.5, so keep using 3.4 in *stable* branches.

[pyramid] set waitress url_scheme to https when base-url scheme is https See https://docs.pylonsproject.org/projects/waitress/en/latest/#using-behind-a-reverse-proxy Since we do not configure trusted_proxy waitress ignore X-Forwarded-Proto header and may generate http urls (pyramid request.url) when the instance is behind a https reverse proxy. This cause cubicweb-signredrequest to not work with since it rely on the url (including scheme). Set url_scheme to 'https' when CubicWeb base-url scheme is https as a workaround.