a tiny workaround for httplib2 redirect bug

[ivishnevs]

if 'location' header is in response object, http2lib try to redirect and use self.request method with body=None argument; this behavior implies a problem like this - #203 and etc.

if response.status in [302, 303]:
redirect_method = "GET"
body = None <--------- (response, content) = self.request(
location, method=redirect_method, body=body,
headers=headers, redirections=redirections - 1)

[codecov-io]

Codecov Report

Merging #214 into master will not impact coverage by -0.2%.

@@ Coverage Diff @@## master #214 +/- ##
=========================================
- Coverage 96.05% 95.86% -0.2% 
=========================================
Files 5 5 Lines 482 484 +2 =========================================
+ Hits 463 464 +1 - Misses 19 20 +1

Impacted Files	Coverage Δ
oauth2/init.py	99.77% <50%> (-0.23%)	❌

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