Merge branch 'gh-webhooks' into 'master'

Avoid that GitHub import fails when retrieving Webhooks for non GitHub admins

Closes #18729 

See merge request !4723

app/views/import/github/status.html.haml

@@ -6,7 +6,7 @@
 
 %p
   %i.fa.fa-warning
-  To import GitHub pull requests, any pull request source branches that had been deleted are temporarily restored on GitHub. To prevent any connected CI services from being overloaded with dozens of irrelevant branches being created and deleted again, GitHub webhooks are temporarily disabled during the import process.
+  To import GitHub pull requests, any pull request source branches that had been deleted are temporarily restored on GitHub. To prevent any connected CI services from being overloaded with dozens of irrelevant branches being created and deleted again, GitHub webhooks are temporarily disabled during the import process, but only if you have admin access to the GitHub repository.
 
 %p.light
   Select projects you want to import.

lib/gitlab/github_import/importer.rb

@@ -66,8 +66,7 @@ module Gitlab
       end
 
       def import_pull_requests
-        hooks = client.hooks(repo).map { |raw| HookFormatter.new(raw) }.select(&:valid?)
-        disable_webhooks(hooks)
+        disable_webhooks
 
         pull_requests = client.pull_requests(repo, state: :all, sort: :created, direction: :asc, per_page: 100)
         pull_requests = pull_requests.map { |raw| PullRequestFormatter.new(project, raw) }.select(&:valid?)
@@ -90,14 +89,14 @@ module Gitlab
         raise Projects::ImportService::Error, e.message
       ensure
         clean_up_restored_branches(branches_removed)
-        clean_up_disabled_webhooks(hooks)
+        clean_up_disabled_webhooks
       end
 
-      def disable_webhooks(hooks)
+      def disable_webhooks
         update_webhooks(hooks, active: false)
       end
 
-      def clean_up_disabled_webhooks(hooks)
+      def clean_up_disabled_webhooks
         update_webhooks(hooks, active: true)
       end
 
@@ -107,6 +106,20 @@ module Gitlab
         end
       end
 
+      def hooks
+        @hooks ||=
+          begin
+            client.hooks(repo).map { |raw| HookFormatter.new(raw) }.select(&:valid?)
+
+          # The GitHub Repository Webhooks API returns 404 for users
+          # without admin access to the repository when listing hooks.
+          # In this case we just want to return gracefully instead of
+          # spitting out an error and stop the import process.
+          rescue Octokit::NotFound
+            []
+          end
+      end
+
       def restore_branches(branches)
         branches.each do |name, sha|
           client.create_ref(repo, "refs/heads/#{name}", sha)