- Use pypi.io as Source url.

- update to 8.1.2:
* Fix a regression on systems with uninitialized locale (:issue:`3575`).
* Use environment markers to filter packages before determining if a
required wheel is supported. Solves (:issue:`3254`).
* Make glibc parsing for `manylinux1` support more robust for the variety of
glibc versions found in the wild (:issue:`3588`).
* Update environment marker support to fully support PEP 508 and legacy
environment markers (:issue:`3624`).
* Always use debug logging to the ``--log`` file (:issue:`3351`).
* Don't attempt to wrap search results for extremely narrow terminal windows
(:issue:`3655`).
* Fix regression with non-ascii requirement files on Python 2 and add support
for encoding headers in requirement files (:issue:`3548`, :pull:`3547`).