Add a custom exception used with build trace locking

lib/gitlab/ci/trace.rb

@@ -16,6 +16,7 @@ module Gitlab
 
       ArchiveError = Class.new(StandardError)
       AlreadyArchivedError = Class.new(StandardError)
+      LockedError = Class.new(StandardError)
 
       attr_reader :job
 
@@ -132,6 +133,8 @@ module Gitlab
 
       def lock(&block)
         in_write_lock(&block)
+      rescue FailedToObtainLockError
+        raise LockedError, "build trace `#{job.id}` is locked"
       end
 
       private

spec/lib/gitlab/ci/trace_spec.rb

@@ -116,7 +116,7 @@ RSpec.describe Gitlab::Ci::Trace, :clean_gitlab_redis_shared_state do
     it 'acquires an exclusive lease on the trace' do
       trace.lock do
         expect { trace.lock }
-          .to raise_error ::Gitlab::ExclusiveLeaseHelpers::FailedToObtainLockError
+          .to raise_error described_class::LockedError
       end
     end
   end