Log Message:
py-pandas: updated to 0.21.0

v0.21.0 Final:

This is a major release from 0.20.3 and includes a number of API changes, \ 
deprecations, new features, enhancements, and performance improvements along \ 
with a large number of bug fixes. We recommend that all users upgrade to this \ 
version.

Highlights include:
* Integration with Apache Parquet, including a new top-level read_parquet \ 
function and DataFrame.to_parquet method, see here.
* New user-facing dtype pandas.api.types.CategoricalDtype for specifying \ 
categoricals independent of the data, see here.
* The behavior of sum and prod on all-NaN Series/DataFrames is now consistent \ 
and no longer depends on whether bottleneck is installed, see here.
* Compatibility fixes for pypy, see here.
* Additions to the drop, reindex and rename API to make them more consistent, \ 
see here.
* Addition of the new methods DataFrame.infer_objects (see here) and \ 
GroupBy.pipe (see here).
* Indexing with a list of labels, where one or more of the labels is missing, is \ 
deprecated and will raise a KeyError in a future version