Error branch is Python 2 code (bytes/str, Windows paths) - by reading #6

Claude reports:

By reading, not run (no Ruby on this machine): the error-handling branch of RubyCheckOnSave.run is Python 2 code and cannot work on ST3/4.

child_process.communicate()[0] returns bytes on Python 3, but the code then calls cmd_output.split('\n') and tests "error" not in line, which raises TypeError on bytes, so the "Ruby syntax error" dialog would never appear when ruby reports an error. It also does first_line.split(':', 2), which on Windows splits C:\path\a.rb:3: syntax error after the drive letter, and goto_line is passed a string line.

Fix: cmd_output = child_process.communicate()[0].decode('utf-8', 'replace'), split with re.match(r'.*?:(\d+): (.*)', line), and pass int(line) to goto_line.