Update Python as per the Zed cycle testing runtime

In the Zed cycle, support and testing for Python versions 3.6 and 3.7
was dropped. [1]

[1] https://governance.openstack.org/tc/reference/runtimes/zed.html

Signed-off-by: Eduardo Santos <eduardo.experimental@gmail.com>
Change-Id: Ia000640a3a6bc33700b27ecf2173954e11237d6d

releasenotes/notes/drop-py36-and-py37-85cf389b2842f045.yaml

@@ -0,0 +1,5 @@
+---
+deprecations:
+  - |
+    Support for Python versions 3.6 and 3.7 was dropped. The minimum supported
+    version is now Python 3.8.

setup.cfg

@@ -6,7 +6,7 @@ description_file =
 author = OpenStack
 author_email = openstack-discuss@lists.openstack.org
 home_page = https://docs.openstack.org/python-manilaclient/latest/
-python_requires = >=3.6
+python_requires = >=3.8
 classifier =
    Development Status :: 5 - Production/Stable
    Environment :: Console
@@ -18,8 +18,6 @@ classifier =
    Programming Language :: Python
    Programming Language :: Python :: 3 :: Only
    Programming Language :: Python :: 3
-   Programming Language :: Python :: 3.6
-   Programming Language :: Python :: 3.7
    Programming Language :: Python :: 3.8
    Programming Language :: Python :: 3.9
 

zuul.d/project.yaml

@@ -2,7 +2,7 @@
     templates:
       - publish-openstack-docs-pti
       - openstack-cover-jobs
-      - openstack-python3-yoga-jobs
+      - openstack-python3-zed-jobs
       - check-requirements
       - release-notes-jobs-python3
     check: