[GH Import] Create an empty wiki if wiki import failed

changelogs/unreleased/4826-github-import-wiki-fix-1.yml

+---
+title: "[GitHub Import] Create an empty wiki if wiki import failed"
+merge_request:
+author:
+type: fixed

lib/gitlab/github_import/importer/repository_importer.rb

@@ -63,6 +63,7 @@ module Gitlab
           true
         rescue Gitlab::Shell::Error => e
           if e.message !~ /repository not exported/
+            project.create_wiki
             fail_import("Failed to import the wiki: #{e.message}")
           else
             true

spec/lib/gitlab/github_import/importer/repository_importer_spec.rb

@@ -11,7 +11,8 @@ describe Gitlab::GithubImport::Importer::RepositoryImporter do
       import_source: 'foo/bar',
       repository_storage_path: 'foo',
       disk_path: 'foo',
-      repository: repository
+      repository: repository,
+      create_wiki: true
     )
   end
 
@@ -192,7 +193,7 @@ describe Gitlab::GithubImport::Importer::RepositoryImporter do
       expect(importer.import_wiki_repository).to eq(true)
     end
 
-    it 'marks the import as failed if an error was raised' do
+    it 'marks the import as failed and creates an empty repo if an error was raised' do
       expect(importer.gitlab_shell)
         .to receive(:import_repository)
         .and_raise(Gitlab::Shell::Error)
@@ -201,6 +202,9 @@ describe Gitlab::GithubImport::Importer::RepositoryImporter do
         .to receive(:fail_import)
         .and_return(false)
 
+      expect(project)
+        .to receive(:create_wiki)
+
       expect(importer.import_wiki_repository).to eq(false)
     end
   end