[pygobject/pygobject-3-34] flake8: fix errors with new flake8 3.8.0

[Christoph Reiter <creiter src gnome org>]

commit 8cfc13a0135ec0fc13ca333e5bf6858740e11d8b
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Sun May 17 23:01:11 2020 +0200

    flake8: fix errors with new flake8 3.8.0

 examples/demo/demos/printing.py | 4 ++--
 tests/test_gobject.py           | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)
---
diff --git a/examples/demo/demos/printing.py b/examples/demo/demos/printing.py
index 6e68037d..a87bd6fd 100644
--- a/examples/demo/demos/printing.py
+++ b/examples/demo/demos/printing.py
@@ -92,8 +92,8 @@ class PrintingApp:
         file_path = print_data['filename']
         if not os.path.isfile(file_path):
             file_path = os.path.join('demos', file_path)
-            if not os.path.isfile:
-                raise Exception("file not found: " % (file_path, ))
+            if not os.path.isfile(file_path):
+                raise Exception("file not found: %s" % (file_path, ))
 
         # in reality you should most likely not read the entire
         # file into a buffer
diff --git a/tests/test_gobject.py b/tests/test_gobject.py
index bba12cb7..1e557de7 100644
--- a/tests/test_gobject.py
+++ b/tests/test_gobject.py
@@ -804,8 +804,8 @@ class TestGValue(unittest.TestCase):
 
 def test_list_properties():
 
-    def find_param(l, name):
-        for param in l:
+    def find_param(props, name):
+        for param in props:
             if param.name == name:
                 return param
         return
@@ -822,8 +822,8 @@ def test_list_properties():
     props = list_props(Gio.SimpleAction)
     assert find_param(props, "enabled")
 
-    def names(l):
-        return [p.name for p in l]
+    def names(props):
+        return [p.name for p in props]
 
     assert (set(names(list_props(Gio.Action))) <=
             set(names(list_props(Gio.SimpleAction))))