Fix syntax issues / unused import reported by static code analysis

pmb/helpers/repo.py

@@ -63,6 +63,4 @@ def diff(args, files_a, files_b=None):
             if add:
                 ret.append(arch + "/" + file)
 
-
-
     return sorted(ret)

test/repo.py

@@ -20,7 +20,6 @@ import os
 import sys
 import pytest
 import types
-import pathlib
 import time
 
 # Import from parent directory
@@ -35,6 +34,7 @@ def args(request, tmpdir):
     args.work = str(tmpdir)
     return args
 
+
 def clear_timestamps_from_files(files):
     """
     Replace all last modified timestamps from pmb.helpers.repo.files() with