Revert of [depot_tools] Find, upload and apply patchset dependencies (patchset #17 id:360001 of https://codereview.chromium.org/1149653002/)

Reason for revert:
Ran into a crash during the bot_update step here:
https://uberchromegw.corp.google.com/i/internal.infra.try/builders/infra-internal-presubmit/builds/62

Original issue's description:
> Find, upload and apply patchset dependencies.
> 
> Here is an explanation of the changes in each module:
> 
> * git_cl.py -
> IF a local branch is being tracked AND a CL has been uploaded there THEN use the CL's issue number and latest patchset as a dependency.
> 
> * upload.py -
> Uploads the patchset dependency, if it exists, to Rietveld (Rietveld will be able to parse this when https://codereview.chromium.org/1155513002/ lands).
> 
> * rietveld.py -
> Adds utility methods to get patchset dependencies from the new Rietveld endpoint (the endpoint will exist when https://codereview.chromium.org/1155513002/ lands).
> 
> * apply_issue.py -
> If CL3 depends on CL2 which in turn depends on CL1 then apply_issue will gather a list of all issues and patchsets to apply (Eg: [CL1:PS1, CL2:PS1, CL3:PS2]).
> apply_issue will then loop over the list applying each dependency.
> Note: The apply_issue.py diff looks much worse than it is. Please see my comment in
> https://codereview.chromium.org/1149653002/diff/260001/apply_issue.py#oldcode169
> 
> 
> Tested end-to-end using a test Git repository (https://skia.googlesource.com/skiabot-test/) and the following CLs created in my test Rietveld instance:
> * https://skia-codereview-staging.appspot.com/931002  ('Branch1 CL')
> * https://skia-codereview-staging.appspot.com/5001001 ('Branch2 CL')
> * https://skia-codereview-staging.appspot.com/9881001 ('Branch3 CL')
> * https://skia-codereview-staging.appspot.com/3951001 ('Branch3.1 CL')
> Opt into the new UI and observe the new 'Depends on Patchset' and 'Dependent Patchsets' sections in the above CLs.
> 
> 
> Design doc is here: https://docs.google.com/document/d/1KZGFKZpOPvco81sYVRCzwlnjGctup71RAzY0MSb0ntc/edit#heading=h.6r6lt4tsvssw
> 
> BUG=502255
> 
> Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=295778

TBR=agable@chromium.org,jrobbins@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=502255

Review URL: https://codereview.chromium.org/1200773003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@295782 0039d316-1c4b-4281-b951-d872f2087c98