Define Trace::ArchiveError to make it explit as an error

lib/gitlab/ci/trace.rb

 module Gitlab
   module Ci
     class Trace
+      ArchiveError = Class.new(StandardError)
+
       attr_reader :job
 
       delegate :old_trace, to: :job
@@ -94,8 +96,8 @@ module Gitlab
       end
 
       def archive!
-        raise 'Already archived' if trace_artifact
-        raise 'Job is not finished yet' unless job.complete?
+        raise ArchiveError, 'Already archived' if trace_artifact
+        raise ArchiveError, 'Job is not finished yet' unless job.complete?
 
         if current_path
           File.open(current_path) do |stream|
@@ -124,7 +126,7 @@ module Gitlab
           temp_path = File.join(dir_path, "job.log")
           FileUtils.touch(temp_path)
           size = IO.copy_stream(src_stream, temp_path)
-          raise 'Not all saved' unless size == src_stream.size
+          raise ArchiveError, 'Failed to copy stream' unless size == src_stream.size
 
           yield(temp_path)
         end

spec/lib/gitlab/ci/trace_spec.rb

@@ -463,11 +463,10 @@ describe Gitlab::Ci::Trace do
 
         context 'when failed to create clone file' do
           before do
-            allow_any_instance_of(described_class)
-              .to receive(:clone_file!).and_raise('Not all saved')
+            allow(IO).to receive(:copy_stream).and_return(0)
           end
 
-          it_behaves_like 'source trace file stays intact', error: 'Not all saved'
+          it_behaves_like 'source trace file stays intact', error: Gitlab::Ci::Trace::ArchiveError
         end
 
         context 'when failed to create job artifact record' do
@@ -494,11 +493,10 @@ describe Gitlab::Ci::Trace do
 
         context 'when failed to create clone file' do
           before do
-            allow_any_instance_of(described_class)
-              .to receive(:clone_file!).and_raise('Not all saved')
+            allow(IO).to receive(:copy_stream).and_return(0)
           end
 
-          it_behaves_like 'source trace in database stays intact', error: 'Not all saved'
+          it_behaves_like 'source trace in database stays intact', error: Gitlab::Ci::Trace::ArchiveError
         end
 
         context 'when failed to create job artifact record' do