Python's urllib falls back to the original request type (scheme).
We decide to insert the original scheme if missing. If the http_proxy environment variable still contains true garbage, then the module still returns garbage.
Coverage increased (+0.07%) to 98.355% when pulling 512d74a8229f7d8485b1e2fa64178b58cb25e0db on prepend-missing-scheme into d19722bb5da086410160a71b8666b0b4081ed224 on master.
Fixes #1
We decide to insert the original scheme if missing. If the http_proxy environment variable still contains true garbage, then the module still returns garbage.