Update python

Changes:

- https://github.com/docker-library/python/commit/cdff21a: Update to 3.8.0rc1, pip 19.2.3
- https://github.com/docker-library/python/commit/7868f53: Fix release candidate folder calculation
- https://github.com/docker-library/python/commit/ca8eac5: Update generated README

library/python

@@ -4,40 +4,40 @@ Maintainers: Tianon Gravi <[email protected]> (@tianon),
              Joseph Ferguson <[email protected]> (@yosifkit)
 GitRepo: https://github.com/docker-library/python.git
 
-Tags: 3.8.0b4-buster, 3.8-rc-buster, rc-buster
-SharedTags: 3.8.0b4, 3.8-rc, rc
+Tags: 3.8.0rc1-buster, 3.8-rc-buster, rc-buster
+SharedTags: 3.8.0rc1, 3.8-rc, rc
 Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, ppc64le, s390x
-GitCommit: 5f5b1bfb9466f0ac8fbd7b615b99493532d42ae8
+GitCommit: cdff21a05616b660073278f13dc560005322349c
 Directory: 3.8-rc/buster
 
-Tags: 3.8.0b4-slim-buster, 3.8-rc-slim-buster, rc-slim-buster, 3.8.0b4-slim, 3.8-rc-slim, rc-slim
+Tags: 3.8.0rc1-slim-buster, 3.8-rc-slim-buster, rc-slim-buster, 3.8.0rc1-slim, 3.8-rc-slim, rc-slim
 Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, ppc64le, s390x
-GitCommit: 5f5b1bfb9466f0ac8fbd7b615b99493532d42ae8
+GitCommit: cdff21a05616b660073278f13dc560005322349c
 Directory: 3.8-rc/buster/slim
 
-Tags: 3.8.0b4-alpine3.10, 3.8-rc-alpine3.10, rc-alpine3.10, 3.8.0b4-alpine, 3.8-rc-alpine, rc-alpine
+Tags: 3.8.0rc1-alpine3.10, 3.8-rc-alpine3.10, rc-alpine3.10, 3.8.0rc1-alpine, 3.8-rc-alpine, rc-alpine
 Architectures: amd64, arm32v6, arm32v7, arm64v8, i386, ppc64le, s390x
-GitCommit: 5f5b1bfb9466f0ac8fbd7b615b99493532d42ae8
+GitCommit: cdff21a05616b660073278f13dc560005322349c
 Directory: 3.8-rc/alpine3.10
 
-Tags: 3.8.0b4-windowsservercore-ltsc2016, 3.8-rc-windowsservercore-ltsc2016, rc-windowsservercore-ltsc2016
-SharedTags: 3.8.0b4-windowsservercore, 3.8-rc-windowsservercore, rc-windowsservercore, 3.8.0b4, 3.8-rc, rc
+Tags: 3.8.0rc1-windowsservercore-ltsc2016, 3.8-rc-windowsservercore-ltsc2016, rc-windowsservercore-ltsc2016
+SharedTags: 3.8.0rc1-windowsservercore, 3.8-rc-windowsservercore, rc-windowsservercore, 3.8.0rc1, 3.8-rc, rc
 Architectures: windows-amd64
-GitCommit: 5f5b1bfb9466f0ac8fbd7b615b99493532d42ae8
+GitCommit: cdff21a05616b660073278f13dc560005322349c
 Directory: 3.8-rc/windows/windowsservercore-ltsc2016
 Constraints: windowsservercore-ltsc2016
 
-Tags: 3.8.0b4-windowsservercore-1803, 3.8-rc-windowsservercore-1803, rc-windowsservercore-1803
-SharedTags: 3.8.0b4-windowsservercore, 3.8-rc-windowsservercore, rc-windowsservercore, 3.8.0b4, 3.8-rc, rc
+Tags: 3.8.0rc1-windowsservercore-1803, 3.8-rc-windowsservercore-1803, rc-windowsservercore-1803
+SharedTags: 3.8.0rc1-windowsservercore, 3.8-rc-windowsservercore, rc-windowsservercore, 3.8.0rc1, 3.8-rc, rc
 Architectures: windows-amd64
-GitCommit: 5f5b1bfb9466f0ac8fbd7b615b99493532d42ae8
+GitCommit: cdff21a05616b660073278f13dc560005322349c
 Directory: 3.8-rc/windows/windowsservercore-1803
 Constraints: windowsservercore-1803
 
-Tags: 3.8.0b4-windowsservercore-1809, 3.8-rc-windowsservercore-1809, rc-windowsservercore-1809
-SharedTags: 3.8.0b4-windowsservercore, 3.8-rc-windowsservercore, rc-windowsservercore, 3.8.0b4, 3.8-rc, rc
+Tags: 3.8.0rc1-windowsservercore-1809, 3.8-rc-windowsservercore-1809, rc-windowsservercore-1809
+SharedTags: 3.8.0rc1-windowsservercore, 3.8-rc-windowsservercore, rc-windowsservercore, 3.8.0rc1, 3.8-rc, rc
 Architectures: windows-amd64
-GitCommit: 5f5b1bfb9466f0ac8fbd7b615b99493532d42ae8
+GitCommit: cdff21a05616b660073278f13dc560005322349c
 Directory: 3.8-rc/windows/windowsservercore-1809
 Constraints: windowsservercore-1809