mail/py-authres: Move MASTER_SITES to CHEESESHOP

[dbaio]

Summary

mail/py-authres: Move MASTER_SITES to CHEESESHOP

Using CHEESESHOP (PyPI) is recommended as the default
MASTER_SITES for Python packages where the distribution
files (sdist) are available there, unless there are
compelling reasons to use an alternative source such
as GitHub, for example if test, data or other important
files are not included due to incorrect packaging or otherwise.

PR:	220257
Reported by:	koobs
Reviewed by:   koobs, garga
Approved by:	garga (mentor), [e-mail] (maintainer)
Differential Revision:	D11343

Test Plan

$ portlint -C: looks fine.

$ rm ../../distfiles/authres-0.900.tar.gz

$ make checksum
===>  License APACHE20 accepted by the user
===>   py27-authres-0.900 depends on file: /usr/local/sbin/pkg - found
=> authres-0.900.tar.gz doesn't seem to exist in /usr/home/dbaio/FreeBSD/ports_head/distfiles/.
=> Attempting to fetch https://pypi.python.org/packages/source/a/authres/authres-0.900.tar.gz
fetch: https://pypi.python.org/packages/source/a/authres/authres-0.900.tar.gz: Not Found
=> Attempting to fetch https://files.pythonhosted.org/packages/source/a/authres/authres-0.900.tar.gz
authres-0.900.tar.gz                          100% of   19 kB  416 kBps 00m00s
===> Fetching all distfiles required by py27-authres-0.900 for building
=> SHA256 Checksum OK for authres-0.900.tar.gz.

• testport: PENDING

[koobs]

I modified the commit log message to include a description for the 'why' (rationale) of the change.