Potential dependency conflicts between appscale-agents and httplib2

[NeolithEra]

Hi, as shown in the following full dependency graph of appscale-agents, appscale-agents requires httplib2 * ， while the installed version of google-api-python-client(1.5.4) requires httplib2 >=0.8,<1dev.

According to Pip's “first found wins” installation strategy, httplib2 0.14.0 is the actually installed version.

Although the first found package version httplib2 0.14.0 just satisfies the later dependency constraint （httplib2 >=0.8,<1dev), it will lead to a build failure once developers release a newer version of httplib2.

Dependency tree--------

appscale-agents - 3.8.1
| +- adal(install version:1.2.2 version range:>=0.4.7)
| +- argparse(install version:1.4.0 version range:*)
| +- azure(install version:2.0.0 version range:==2.0.0)
| +- azure-mgmt-marketplaceordering(install version:0.2.1 version range:*)
| +- boto(install version:2.49.0 version range:*)
| +- cryptography(install version:2.8 version range:*)
| +- google-api-python-client(install version:1.5.4 version range:==1.5.4)
| | +- httplib2(install version:0.14.0 version range:>=0.8,<1dev)
| | +- oauth2client(install version:4.0.0 version range:<5.0.0dev,>=1.5.0)
| | | +- httplib2(install version:0.14.0 version range:>=0.9.1)
| | | +- pyasn1(install version:0.4.8 version range:>=0.1.7)
| | | +- pyasn1-modules(install version:0.2.7 version range:>=0.0.5)
| | | +- rsa(install version:4.0 version range:>=3.1.4)
| | | | +- pyasn1(install version:0.4.8 version range:>=0.1.3)
| | | +- six(install version:1.13.0 version range:>=1.6.1)
| | +- six(install version:1.13.0 version range:>=1.6.1,<2dev)
| | +- uritemplate(install version:3.0.1 version range:<4dev,>=3.0.0)
| +- httplib2(install version:0.14.0 version range:*)
| +- keyring(install version:18.0.1 version range:>=12.0.2,<19.0.0)
| +- keyrings.alt(install version:3.1.1 version range:>=3.1,<3.2)
| +- keyrings.alt(install version:3.1.1 version range:<3.2,>=3.1)
| +- msrestazure(install version:0.4.34 version range:==0.4.34)
| +- oauth2client(install version:4.0.0 version range:==4.0.0)
| | +- httplib2(install version:0.14.0 version range:>=0.9.1)
| | +- pyasn1(install version:0.4.8 version range:>=0.1.7)
| | +- pyasn1-modules(install version:0.2.7 version range:>=0.0.5)
| | +- rsa(install version:4.0 version range:>=3.1.4)
| | | +- pyasn1(install version:0.4.8 version range:>=0.1.3)
| | +- six(install version:1.13.0 version range:>=1.6.1)
| +- PyYAML(install version:5.2b1 version range:*)
| +- requests(install version:2.22.0 version range:>=2.20.0)
| | +- certifi(install version:2019.9.11 version range:>=2017.4.17)
| | +- chardet(install version:3.0.4 version range:<3.1.0,>=3.0.2)
| | +- idna(install version:2.8 version range:>=2.5,<2.9)
| | +- urllib3(install version:1.25.7 version range:<1.26,>=1.21.1)
| +- retrying(install version:1.3.3 version range:==1.3.3)
| | +- six(install version:1.13.0 version range:>=1.7.0)
| +- setuptools(install version:33.1.1 version range:<34,>=11.3)
| +- soappy(install version:0.12.22 version range:*)
| +- tabulate(install version:0.7.7 version range:==0.7.7)
| +- termcolor(install version:1.1.0 version range:*)
| +- wstools(install version:0.4.3 version range:==0.4.3)
| | +- docutils(install version:0.15.2 version range:*) 

Thanks for your attention.
Best,
Neolith

[NeolithEra]

Suggested Solution

1. Fix your direct dependencies to be httplib2 <1dev.
2. Ask your upstream project google-api-python-client to loose the version range of httplib2 to be >=0.9.2.

@whoarethebritons Which solution do you prefer, 1 or 2?
Please let me know your choice. May I pull a request to solve this issue?