ALBS-732: pungi: do not build anything if unsigned packages found

- Some tiny changes (pep8 & stronger condition)

pungi/phases/pkgset/pkgsets.py

@@ -974,7 +974,7 @@ class KojiMockPackageSet(PackageSetBase):
         with open(rpm_path, 'rb') as fd:
             header = ts.hdrFromFdno(fd)
             signature = header[rpm.RPMTAG_SIGGPG] or header[rpm.RPMTAG_SIGPGP]
-            if not signature:
+            if signature is None:
                 return False
             pgp_msg = pgpy.PGPMessage.from_blob(signature)
             return any(
@@ -985,8 +985,8 @@ class KojiMockPackageSet(PackageSetBase):
     def get_package_path(self, queue_item):
         rpm_info, build_info = queue_item
 
-        # Check if this RPM is coming from scratch task. In this case, we already
-        # know the path.
+        # Check if this RPM is coming from scratch task.
+        # In this case, we already know the path.
         if "path_from_task" in rpm_info:
             return rpm_info["path_from_task"]