Remove vendored Requests

[Jamim]

Hi everyone,

The documentation says that vendored versions of requests and urllib3 are no longer being used and have been replaced with a direct dependency on upstream urllib3 and requests is no longer a dependency of botocore.

However, the requests is no longer a dependency of botocore statement is not true currently, since requests is used in botocore/exceptions.py and in tests.

I believe it's time to remove vendored requests.

This PR closes #1122, closes #1608, closes #1615, and closes jantman/awslimitchecker#421.

[codecov-io]

Codecov Report

Merging #1817 into develop will increase coverage by 0.03%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #1817      +/-   ##
===========================================
+ Coverage    92.51%   92.54%   +0.03%     
===========================================
  Files           53       53              
  Lines         9958     9958              
===========================================
+ Hits          9213     9216       +3     
+ Misses         745      742       -3

Impacted Files	Coverage Δ
botocore/endpoint.py	98.58% <ø> (ø)	⬆️
botocore/exceptions.py	99.39% <100%> (ø)	⬆️
botocore/credentials.py	98.85% <0%> (+0.34%)	⬆️

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[Jamim]

Hello @jamesls,
Could you please take a look at this PR?
Thank you!

[jamesls]

Hi, thanks for the PR. We won't be able to remove the entire requests directory. We want to keep the exceptions in place in order to help with backwards compatibility.

Additionally, some of the changes in here won't work as is. For example in the exceptions.py the imports to vendored requests are removed but replaced with a direct dependency on requests (https://github.com/boto/botocore/pull/1817/files#diff-7768fbeb174f209a8fc3ed77a823ac1c). We explicitly do not want to depend on requests (only urllib3) and this won't fix the reason they were left in the first place (to preserve backwards compatibility for people catching those vendored exceptions).

To help speed this along, I've gone ahead and added a PR that I think this is a compromise that can make everyone happy:

• Remove all the requests/urllib3 code with the exception of the exception classes
• Update the tests to not use vendored requests unless specifically testing backwards compatibility related to vendored requests.

Let me know if you have any questions or concerns.