image-buildinfo: Update to python3 syntax

(From OE-Core rev: 6e7d9dd9b5cbf46b955036876a25353fafbf264c)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/image-buildinfo.bbclass

@@ -32,7 +32,7 @@ def get_layer_git_status(path):
                                 shell=True,
                                 stderr=subprocess.STDOUT)
         return ""
-    except subprocess.CalledProcessError, ex:
+    except subprocess.CalledProcessError as ex:
         # Silently treat errors as "modified", without checking for the
         # (expected) return code 1 in a modified git repo. For example, we get
         # output and a 129 return code when a layer isn't a git repo at all.