remove mailchimp tracking

ENT-2384: Invoke learner transmission task only for enterprise learners

Fixed - " AttributeError: 'str' object has no attribute 'decode' " - BOM-922

Invoke learner transmission task only for enterprise learners
ENT-2384

added docstring

Fixed brokent unit test

BOM-925

BOM Project Xblock Recommber integration tests fix

Fixing TypeError, the JSON object must be str, not 'bytes'.

BOM-924

Fixing TypeError, the JSON object must be str, not 'bytes'.

Python3 json can not work with bytes type input so used simplejson
instead of python json which works with both bytes and unicode
type input.
Previously we mistakenly updated StringIO to six.String io. which
caused the tests failure. Used io.BytesIO to fix the issues as
assci character bytes can not be converted to unicode.

BOM fix remaining capa module issues

Removed encode method to fix input to csv write method - BOM-837

BOM-805

removed unnecessary encode method to fix input to csv write method

python3 compatibility: Before comparison with unicode decode text if its type is bytes.

BOM-898 fix test_responsetypes.py issues
Updated safe_exec to use random2 library instead of random.
As python3 random generates different results as compared to
python2, which causes a lot of test failures and if we use
python3 random and fix tests it will cause state invalidation
of capa problems, So random2 was uses to make the behaviour same
in python3.

BOM-899 name xrange is not defined
xrange is used in safe_exec and there might be old courses where
this is being used in capa problems. All those tests fail in python3
as this was renamed to range. Used six.moves.xrange so that code
works for python3 and if there is any old code using xrange it
works too.

BOM-804

Updated the items order in response list comparison to work with both python versions - BOM-819

BOM-917

BOM-916

Remove backtick typo in advanced_entry.underscore

Feanil/fix perf pins

We also pin back edx-lint to fix a regression we introduced when we
started having to roll back all the requirements changes.

DISCO-188 publisher link

Don't try to show anonymous users the first-purchase discount

Fix encoding issue.

Add publisher link to settings dropdown if the features setting
is set.

Fixed double decoding issue.
Fixed the mock.assertMethod. Dict keys were coming different order.

Upgrade python 3 decode error

Remove YouTube logo from footer.

python3 compatibility
we only need to decode if the xml is bytes