Allow binary files to be copied into the build context

src/rocker/core.py

@@ -422,7 +422,8 @@ def write_files(extensions, args_dict, target_directory):
  'and cannot be written out, skipping' % (file_path, active_extension.get_name()))
  continue
  Path(os.path.dirname(full_path)).mkdir(exist_ok=True, parents=True)
- with open(full_path, 'w') as fh:
+ mode = 'wb' if isinstance(contents, bytes) else 'w' # check to see if contents should be written as binary
+ with open(full_path, mode) as fh:
  print('Writing to file %s' % full_path)
  fh.write(contents)
  return all_files