Handle errors when removing a runner

A QA test failed in staging while trying to remove a runner, but it's
not clear why. This adds error handling to provide some feedback.

qa/qa/resource/project.rb

@@ -115,8 +115,8 @@ module QA
         post_body
       end
 
-      def runners
-        response = get Runtime::API::Request.new(api_client, api_runners_path).url
+      def runners(tag_list: nil)
+        response = get Runtime::API::Request.new(api_client, "#{api_runners_path}?tag_list=#{tag_list.compact.join(',')}").url
         parse_body(response)
       end
 

qa/qa/resource/runner.rb

@@ -41,7 +41,17 @@ module QA
       end
 
       def remove_via_api!
-        @id = project.runners.find { |runner| runner[:description] == name }[:id]
+        runners = project.runners(tag_list: tags)
+        unless runners && !runners.empty?
+          raise "Project #{project.path_with_namespace} has no runners with tags #{tags}."
+        end
+
+        this_runner = runners.find { |runner| runner[:description] == name }
+        unless this_runner
+          raise "Project #{project.path_with_namespace} does not have a runner with a description matching #{name} and tags #{tags}. Runners available: #{runners}"
+        end
+
+        @id = this_runner[:id]
 
         super