Dependencies are lowercased before being pip-installed

[Cheaterman]

Hi,

Dependencies are being lowercased before being pip-installed (well, written in the temporary requirements.txt file). This is an issue when trying to use eg GitLab deploy tokens to access a private library (it lowercases the token).

I might try a PR if I have the time/chance, otherwise I'm just leaving this here so that we can keep it in mind.

[Julian-O]

See also: #2062