Fix errors when pushing with an expired license

When a user pushed to a GitLab EE license that had an expired license,
it would fail with one of two errors:

In the current GitLab 13.1 branch it would show:

```
undefined method `license_message' for LicenseHelper:Module
```

However, previous versions would show:

```
undefined method `full_sanitizer' for Gitlab::GitAccess:Class
```

The latter error occurred because the view helper strip_tags only works
in a view. We now explicitly define `strip_tags` to use the same
sanitizer.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/217031

ee/changelogs/unreleased/sh-fix-issue-217031.yml

+---
+title: Fix errors when pushing with an expired license
+merge_request: 34458
+author:
+type: fixed

ee/lib/ee/gitlab/git_access.rb

@@ -5,8 +5,8 @@ module EE
     module GitAccess
       prepend GeoGitAccess
       extend ::Gitlab::Utils::Override
-      include ActionView::Helpers::SanitizeHelper
       include PathLocksHelper
+      include SubscribableBannerHelper
 
       override :check
       def check(cmd, changes)
@@ -98,11 +98,15 @@ module EE
 
       def check_if_license_blocks_changes!
         if ::License.block_changes?
-          message = ::LicenseHelper.license_message(signed_in: true, is_admin: (user && user.admin?))
+          message = license_message(signed_in: true, is_admin: (user && user.admin?))
           raise ::Gitlab::GitAccess::ForbiddenError, strip_tags(message)
         end
       end
 
+      def strip_tags(html)
+        Rails::Html::FullSanitizer.new.sanitize(html)
+      end
+
       override :check_size_limit?
       def check_size_limit?
         strong_memoize(:check_size_limit) do

ee/spec/lib/gitlab/git_access_spec.rb

@@ -600,6 +600,18 @@ RSpec.describe Gitlab::GitAccess do
         end
       end
 
+      context "when license blocks changes" do
+        before do
+          create_current_license(starts_at: 1.month.ago.to_date, block_changes_at: Date.current, notify_admins_at: Date.current)
+          user.update_attribute(:admin, true)
+          project.add_role(user, :developer)
+        end
+
+        it 'raises an error' do
+          expect { push_changes(changes[:any]) }.to raise_error(Gitlab::GitAccess::ForbiddenError, /Your subscription will expire/)
+        end
+      end
+
       context "group-specific access control" do
         let(:user) { create(:user) }
         let(:group) { create(:group) }