build_info: Fix parsing of versions with no flavor

Author: ben-clayton

build_info.py

@@ -100,12 +100,15 @@ def deduce_software_version(directory):
         for line in f.readlines():
             match = pattern.match(line)
             if match:
+                flavor = match.group(4)
+                if flavor == None:
+                    flavor = ""
                 return {
                     "major": match.group(1),
                     "minor": match.group(2),
                     "patch": match.group(3),
-                    "flavor": match.group(4).lstrip("-"),
-                    "-flavor": match.group(4),
+                    "flavor": flavor.lstrip("-"),
+                    "-flavor": flavor,
                     "date": match.group(5),
                 }
     raise Exception('No version number found in {}'.format(changes_file))