client: simplify loop exit logic

Simplify the loop exit logic in _get_target_file() to simply return a
verified file_object, once we have it, rather than breaking from the loop
and then returning the file_object.

This converts a use of a try/except/else to a try/except and is a little
easier to read.

Signed-off-by: Joshua Lock <jlock@vmware.com>

tuf/client/updater.py

@@ -1327,23 +1327,18 @@ def _get_target_file(self, target_filepath, file_length, file_hashes,
  # Verify 'file_object' against the expected length and hashes.
  self._check_file_length(file_object, file_length)
  self._check_hashes(file_object, file_hashes)
+ # If the file verifies, we don't need to try more mirrors
+ return file_object
 
  except Exception as exception:
  # Remember the error from this mirror, and "reset" the target file.
  logger.debug('Update failed from ' + file_mirror + '.')
  file_mirror_errors[file_mirror] = exception
  file_object = None
 
- else:
- break
-
- if file_object:
- return file_object
-
- else:
- logger.debug('Failed to update ' + repr(target_filepath) + ' from'
- ' all mirrors: ' + repr(file_mirror_errors))
- raise tuf.exceptions.NoWorkingMirrorError(file_mirror_errors)
+ logger.debug('Failed to update ' + repr(target_filepath) + ' from'
+ ' all mirrors: ' + repr(file_mirror_errors))
+ raise tuf.exceptions.NoWorkingMirrorError(file_mirror_errors)