sqlite related stuff as part of making sqlite the canonical backend

* Module.py __init__ sets up sqlite db connection by default
* Module.py __init__ calls init_db() which is empty, expects subclasses to implement as necessary
* Module.py doesn't close sqlite connection by default

Changes call for a couple updates in Karma.py, namely implementing db_init
and excepting sqlite3.Error rather than closing the connection

Module.py

@@ -44,6 +44,14 @@ class Module(object):
         self.server = server
         self.modlist = modlist
 
+        # open database connection
+        dbfile = self.config.get('dr.botzo', 'database')
+        self.conn = sqlite3.connect(dbfile)
+        self.conn.row_factory = sqlite3.Row
+
+        # set up database for this module
+        self.db_init()
+
         # add self to the object list
         modlist.append(self)
 
@@ -295,15 +303,14 @@ class Module(object):
         See also db_module_registered, below.
         """
 
-        dbfile = self.config.get('dr.botzo', 'database')
-        conn = sqlite3.connect(dbfile)
-        return conn
+        return self.conn
 
     def db_module_registered(self, modulename):
         """
         ask the database for a version number for a module. Return that version
         number if the module has registered, or None if not
         """
+
         conn = self.get_db()
         version = None
         try:
@@ -313,9 +320,16 @@ class Module(object):
             version = cur.fetchone()
             if (version != None):
                 version = version[0]
-        finally: conn.close()
+        except sqlite3.Error as e:
+            print("sqlite error:" + str(e))
+
         return version
 
+    def db_init(self):
+        """
+        Set up the database tables and so on, if subclass is planning on using it.
+        """
+
     def do(self, connection, event, nick, userhost, replypath, what, admin_unlocked):
         """
         Do the primary thing this module was intended to do.

modules/Karma.py

@@ -17,6 +17,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 """
 
 import re
+import sqlite3
 
 from Module import Module
 
@@ -39,6 +40,7 @@ class Karma(Module):
         self.karmare = re.compile(karmapattern)
         self.queryre = re.compile(querypattern)
 
+    def db_init(self):
         # need to init the database if karma tables don't already exist
         version = self.db_module_registered(self.__class__.__name__)
         if (version == None):
@@ -65,7 +67,10 @@ class Karma(Module):
                 sql = 'INSERT INTO drbotzo_modules VALUES (?,?)'
                 conn.execute(sql, (self.__class__.__name__, 1))
                 conn.commit()
-            finally: conn.close()
+            except sqlite3.Error as e:
+                conn.rollback()
+                print("sqlite error: " + str(e))
+                raise
 
     def do(self, connection, event, nick, userhost, replypath, what, admin_unlocked):
         """look for karma strings at the start of messages"""
@@ -96,7 +101,9 @@ class Karma(Module):
             '''
             conn.execute(sql, (key, value, nick, userhost))
             conn.commit()
-        finally: conn.close()
+        except sqlite3.Error as e:
+            conn.rollback()
+            return self.reply(connection, replypath, "sqlite error: " + str(e))
 
     def handle_karma_query(self, connection, nick, userhost, replypath, what):
         match = self.queryre.match(what)
@@ -121,8 +128,8 @@ class Karma(Module):
 
                 reply = '{nick}: {key} has {value[0]!s} points of karma (rank {rank})'.format(
                     nick=nick, key=key, value=value, rank=rank)
-
-        finally: conn.close()
+        except sqlite3.Error as e:
+            return self.reply(connection, replypath, "sqlite error: " + str(e))
 
         self.reply(connection, replypath, reply)