API: raise on setops for + and - for Indexes (GH8226)
Provides a link to the list of encoding in Python

Better links

Added link to standard encodings in io html documentation

Removed link to Python2 documentations and left link to Python3 only
Merge pull request #8227 from jreback/index_api

API: raise on setops for + and - for Indexes (GH8226)
Merge pull request #8125 from dxshank/dev-update-read-csv-docs

DOC: Link to Python standard encodings from read_csv documentation
BUG: Change AssertionError to ValueError
TST: Change tests to check for ValueError

Two tests call OLS with clustering and Newey-West adjustment, which does
not work properly per GH5884. Change them to test for the ValueError
that is now raised when OLS is called in this way.
Merge remote-tracking branch 'upstream/master'