Handle database locking errors.

MosDb.py

@@ -1,4 +1,5 @@
 from datetime import datetime
+from time import sleep
 import sqlite3
 
 class MosDb():
@@ -63,6 +64,8 @@ class MosDb():
         """Converts given local time to UTC unix stamp
         For SQLite queries, use strftime('%s', '2017-03-08T17:46:52', 'utc')
         """
+        if datestring is None:
+            return None
         dt = datetime.strptime(datestring, "%Y-%m-%dT%H:%M:%S")
         return dt.timestamp()
 
@@ -86,10 +89,17 @@ class MosDb():
         
         fieldsList   = ", ".join(fieldsList)
         placeHolders = ", ".join(placeHolders)
-        self.c.execute(
-            "INSERT OR REPLACE INTO " + table + " (" + fieldsList + ") VALUES (" + placeHolders + ")",
-            valuesTuple
-        )
+        dataWrittenOk = False
+        while not dataWrittenOk:
+            try:
+                self.c.execute(
+                    "INSERT OR REPLACE INTO " + table + " (" + fieldsList + ") VALUES (" + placeHolders + ")",
+                    valuesTuple
+                )
+                dataWrittenOk = True
+            except sqlite3.OperationalError as e:
+                print("OpErr: {} - retrying.".format(e))
+                sleep(0.5)
         self.changes_made = True
 
     def mark_deleted(self, objData):