Treat git commands as failed if output has errors

This also adds a better failure message when the push options tests
fail to create an MR.

qa/qa/git/repository.rb

@@ -224,7 +224,7 @@ module QA
         alias_method :to_s, :response
 
         def success?
-          exitstatus == 0
+          exitstatus == 0 && !response.include?('Error encountered')
         end
       end
 

qa/qa/specs/features/api/3_create/merge_request/push_options_labels_spec.rb

@@ -30,6 +30,7 @@ module QA
 
         merge_request = project.merge_request_with_title(title)
 
+        expect(merge_request).not_to be_nil, "There was a problem creating the merge request"
         expect(merge_request[:labels]).to include('one').and include('two').and include('three')
       end
 
@@ -49,6 +50,8 @@ module QA
 
           merge_request = project.merge_request_with_title(title)
 
+          expect(merge_request).not_to be_nil, "There was a problem creating the merge request"
+
           aggregate_failures do
             expect(merge_request[:labels]).to include('two')
             expect(merge_request[:labels]).not_to include('one')

qa/qa/specs/features/api/3_create/merge_request/push_options_mwps_spec.rb

@@ -60,6 +60,8 @@ module QA
 
         merge_request = project.merge_request_with_title(title)
 
+        expect(merge_request).not_to be_nil, "There was a problem creating the merge request"
+
         merge_request = Resource::MergeRequest.fabricate_via_api! do |mr|
           mr.project = project
           mr.id = merge_request[:iid]
@@ -101,6 +103,7 @@ module QA
 
         merge_request = project.merge_request_with_title(title)
 
+        expect(merge_request).not_to be_nil, "There was a problem creating the merge request"
         expect(merge_request[:merge_when_pipeline_succeeds]).to be true
 
         merge_request = Support::Waiter.wait_until(sleep_interval: 5) do

qa/qa/specs/features/api/3_create/merge_request/push_options_remove_source_branch_spec.rb

@@ -30,6 +30,8 @@ module QA
 
         merge_request = project.merge_request_with_title(title)
 
+        expect(merge_request).not_to be_nil, "There was a problem creating the merge request"
+
         merge_request = Resource::MergeRequest.fabricate_via_api! do |mr|
           mr.project = project
           mr.id = merge_request[:iid]

qa/qa/specs/features/api/3_create/merge_request/push_options_target_branch_spec.rb

@@ -38,6 +38,7 @@ module QA
 
         merge_request = project.merge_request_with_title(title)
 
+        expect(merge_request).not_to be_nil, "There was a problem creating the merge request"
         expect(merge_request[:target_branch]).to eq(target_branch)
 
         merge_request = Resource::MergeRequest.fabricate_via_api! do |mr|

qa/qa/specs/features/api/3_create/merge_request/push_options_title_description_spec.rb

@@ -30,6 +30,8 @@ module QA
 
         merge_request = project.merge_request_with_title(title)
 
+        expect(merge_request).not_to be_nil, "There was a problem creating the merge request"
+
         aggregate_failures do
           expect(merge_request[:title]).to eq(title)
           expect(merge_request[:description]).to eq(description)