<2.0dev isnot a valid version matcher in the sense ofPEP 440.
(Edit: it is after all valid, just hidden in the specification, and distlib doesn't parse it)

The canonical public version identifiers MUST comply with the following scheme:
[N!]N(.N)*[{a|b|rc}N][.postN][.devN]

It is also considered bad practice to have an upper bound on package versions and installers like pip do not typically consider development versions in any case (unless explicitly told to).

See:googleapis/google-api-python-client#2151