Move "custom" functionality from conan codebase

[lasote]

Fix here, remove there.

[uilianries]

Verifying the code present in Conan and the code which was merged to python-patch-ng, I can say we don't need to get anything from Conan codebase to here.

To be more precise, the PR techtonik#41 is enough to replace our workaround which I've removed here: conan-io/conan@1ac364b