BUG: render dataframe as html do not produce duplicate element id's (pandas-dev#16780) (pandas-dev#16801)

* BUG: when rendering dataframe as html do not produce duplicate element id's pandas-dev#16780

* CLN: removing spaces in code causes pylint check to fail

* DOC: moved whatsnew comment to 0.20.3 release from 0.21.0

Author: ri938

doc/source/whatsnew/v0.20.3.txt

@@ -42,9 +42,10 @@ Bug Fixes
 - Fixed compat with loading a ``DataFrame`` with a ``PeriodIndex``, from a ``format='fixed'`` HDFStore, in Python 3, that was written in Python 2 (:issue:`16781`)
 - Fixed a bug in failing to compute rolling computations of a column-MultiIndexed ``DataFrame`` (:issue:`16789`, :issue:`16825`)
 - Bug in a DataFrame/Series with a ``TimedeltaIndex`` when slice indexing (:issue:`16637`)
-- Bug in reindexing on an empty ``CategoricalIndex`` (:issue:`16770`)
 - Fixed a pytest marker failing downstream packages' tests suites (:issue:`16680`)
 - Fixed compat with loading a ``DataFrame`` with a ``PeriodIndex``, from a ``format='fixed'`` HDFStore, in Python 3, that was written in Python 2 (:issue:`16781`)
+- Fixed a pytest marker failing downstream packages' tests suites (:issue:`16680`)
+- Bug in reindexing on an empty ``CategoricalIndex`` (:issue:`16770`)
 
 Conversion
 ^^^^^^^^^^