Does not warn or error on conflicting version requirements

[Diggsey]

For example, if the pipfile specifies a dependency with version <=2.5.1, while the same package also occurs as a transitive dependency with version >=2.6.0, then both pipfile and pipfile.lock will agree that the version is 2.5.1, but it will silently install 2.6.0 in the virtualenv, without showing any warnings or errors about the conflicting requirements.

[nateprewitt]

Hey @Diggsey, thanks for checking in on this. We're currently aware of this and tracking the progress in #298. We have an open PR that will attempt to make this a little less subtle, but there are a couple snags that still haven't been resolved. pip itself doesn't actually handle the transitive dependency problem, but pipenv's behaviour is currently even more out of line than pip. We'll hopefully have this sorted in a future release.