Log Message:
(devel/py-pbr) updated 5.1.3 to 5.2.1

  5.2.1
  -----
  * Add openstack-tox-py37 job
  * Set subparser argument required
  * Remove neutron-lbaas
  * Update Sphinx requirement
  * Fix white space handling in file names

  5.2.0
  -----
  * OpenDev Migration Patch
  * Typo fix: s/extract\_mesages/extract\_messages/
  * Support provides\_extra metadata
  * Replace openstack.org git:// URLs with https://
  * Fix nits and typos on release note message
  * Remove libzmq-dev from integration.sh package install
  * Fix error when keywords are defined as a list in cfg