findmissing: Open databases with charset='utf8mb4'

Sometimes characters in commit messages are encoded in utf8mb4.
Open database accordingly.

Unrelated changes mandated by repo:
- Disable useless MySQLdb import errors
- Remove 'object' from 'Fix' class definition in initdb_upstream.py

BUG=None
TEST=Run tool and verify that all commits are supported

Change-Id: I492c1fd117da0f613b9a943c6569a20775c064cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2606647
Reviewed-by: Curtis Malainey <cujomalainey@chromium.org>
Commit-Queue: Guenter Roeck <groeck@chromium.org>
Tested-by: Guenter Roeck <groeck@chromium.org>
diff --git a/contrib/findmissing/getopen.py b/contrib/findmissing/getopen.py
index 74cbea3..30068c6 100755
--- a/contrib/findmissing/getopen.py
+++ b/contrib/findmissing/getopen.py
@@ -224,7 +224,8 @@
 
     synchronize.synchronize_repositories(True)
 
-    db = MySQLdb.Connect(user='linux_patches_robot', host='127.0.0.1', db='linuxdb')
+    db = MySQLdb.Connect(user='linux_patches_robot', host='127.0.0.1', db='linuxdb',
+                         charset='utf8mb4')
 
     if branch:
         report_integration_status_branch(db, metadata, handled_shas, branch, conflicts)