Revise version constraint of httplib2, to avoid potential dependency conflicts

[NeolithEra]

Hi, as shown in the following full dependency graph of app-engine-start-vm, app-engine-start-vm requires httplib2 (the latest version)， while the installed version of google-api-python-client(1.7.10) requires httplib2>=0.9.2,<1dev.

According to Pip's “first found wins” installation strategy, httplib2 0.13.1 is the actually installed version.

Although the first found package version httplib2 0.13.1 just satisfies the later dependency constraint (httplib2>=0.9.2,<1dev), it will lead to a build failure once developers release a newer version of httplib2.

Dependency tree--------

app-engine-start-vm(version range:)
| +-flask(version range:==0.12)
| +-google-api-python-client(version range:)
| | +-httplib2(version range:>=0.9.2,<1dev)
| | +-google-auth(version range:>=1.4.1)
| | +-google-auth-httplib2(version range:>=0.0.3)
| | +-six(version range:>=1.6.1,<2dev)
| | +-uritemplate(version range:>=3.0.0,<4dev)
| +-httplib2(version range:)
| +-oauth2client(version range:)
| | +-httplib2(version range:>=0.9.1)
| | +-pyasn1(version range:>=0.1.7)
| | +-pyasn1-modules(version range:>=0.0.5)
| | +-rsa(version range:>=3.1.4)
| | +-six(version range:>=1.6.1)

Thanks for your attention.
Best,
Neolith

[NeolithEra]

Solution

1. Fix your direct dependencies to be httplib2>=0.9.2,<1dev and google-api-python-client==1.7.10, to remove this conflict.
   I have checked this revision will not affect your downstream projects now.

2. Remove your direct dependency httplib2 and use the httplib2 transitively introduced by google-api-python-client.

@fivunlm Please let me know your choice. I can submit a PR to fix this issue.

Build a good dependency ecosystem for python projects is our common goal ^_^.