Merge branch 'bug/rst-disable-patch' into 'master'

Use forked github-markup gem

To use the forked version, we must undo some patching we did before.

I'm preserving one patch that changes the interpreter from `python2` to `python3` so that we don't change the required libraries for current source installs. This will let us release the change in a patch release instead of waiting for `8.13`.

Related issue: gitlab-org/gitlab-ce#21696

See merge request !1015

config/patches/gitlab-rails/github-markup_gem-rest2html.patch

@@ -1,19 +0,0 @@
-diff --git a/lib/github/commands/rest2html b/lib/github/commands/rest2html
-index 7ecfe27..958cd3c 100755
---- a/lib/github/commands/rest2html
-+++ b/lib/github/commands/rest2html
-@@ -31,9 +31,11 @@ import sys
- import os
-
- # This fixes docutils failing with unicode parameters to CSV-Table. The -S
--# switch and the following 2 lines can be removed after upgrading to python 3.
--reload(sys)
--sys.setdefaultencoding('utf-8')
-+# switch and the following 3 lines can be removed after upgrading to python 3.
-+if sys.version_info[0] < 3:
-+    reload(sys)
-+    sys.setdefaultencoding('utf-8')
-+
- import site
-
- try:

config/software/gitlab-rails.rb

@@ -71,8 +71,7 @@ build do
 
   # This patch makes the github-markup gem use and be compatible with Python3
   # We've sent part of the changes upstream: https://github.com/github/markup/pull/919
-  patch source: 'github-markup_gem-markups.patch', target: "#{gems_directory}/github-markup-1.4.0/lib/github/markups.rb"
-  patch source: 'github-markup_gem-rest2html.patch', target: "#{gems_directory}/github-markup-1.4.0/lib/github/commands/rest2html"
+  patch source: 'gitlab-markup_gem-markups.patch', target: "#{gems_directory}/gitlab-markup-1.5.0/lib/github/markups.rb"
 
   # In order to precompile the assets, we need to get to a state where rake can
   # load the Rails environment.