Very minor DB-API compliance fixes.

MySQLdb/MySQLdb/cursors.py

@@ -29,7 +29,7 @@ class BaseCursor(object):
         self.connection = connection
         self.description = None
         self.rowcount = -1
-        self.arraysize = 100
+        self.arraysize = 1
         self._executed = None
         self.lastrowid = None
         self.messages = []

MySQLdb/_mysql.c

@@ -609,6 +609,10 @@ _mysql_ConnectionObject_close(
 		mysql_close(&(self->connection));
 		Py_END_ALLOW_THREADS
 		self->open = 0;
+	} else {
+		PyErr_SetString(_mysql_ProgrammingError,
+				"closing a closed connection");
+		return NULL;
 	}
 	_mysql_ConnectionObject_clear(self);
 	Py_INCREF(Py_None);