MySQL backend fixes for Python 3.

With Python 2, text sent to and from MySQL is treated as bytes in
Python.  The database may be recorded by MySQL as having some other
encoding (latin1 being the default in some MySQL versions - Roundup
does not set an encoding explicitly, unlike in back_postgresql), but
as long as MySQL's notion of the connection encoding agrees with its
notion of the database encoding, no conversions actually take place
and the bytes are stored and returned as-is.

With Python 3, text sent to and from MySQL is treated as Python
Unicode strings.  When the database and connection encoding is latin1,
that means the bytes stored in the database under Python 2 are
interpreted as latin1 and converted from that to Unicode, producing
incorrect results for any non-ASCII characters; furthermore, if trying
to store new non-ASCII data in the database under Python 3, any
non-latin1 characters produce errors.

This patch arranges for both the connection and database character
sets to be UTF-8 when using Python 3, and documents a need to export
and import the database when moving from Python 2 to Python 3 with
this backend.

Author: jsm28

doc/upgrading.txt

@@ -44,13 +44,15 @@ Python 3 support
 Many of the ``.html`` and ``.py`` files from Roundup that are copied
 into tracker directories have changed for Python 3 support.  If you
 wish to move an existing tracker to Python 3, you need to merge in
-those changes.  If your tracker uses the ``anydbm`` backend, you also
-need to export the tracker contents using ``roundup-admin export``
-running under Python 2, and them import them using ``roundup-admin
-import`` running under Python 3, as for a migration to a different
-backend.  If using the ``sqlite`` backend, you do not need to export
-and import, but need to delete the ``db/otks`` and ``db/sessions``
-files when changing Python version.
+those changes.  If your tracker uses the ``anydbm`` or ``mysql``
+backends, you also need to export the tracker contents using
+``roundup-admin export`` running under Python 2, and them import them
+using ``roundup-admin import`` running under Python 3, as for a
+migration to a different backend.  If using the ``sqlite`` backend,
+you do not need to export and import, but need to delete the
+``db/otks`` and ``db/sessions`` files when changing Python version.
+If using the ``postgresql`` backend, you do not need to export and
+import and no other special database-related steps are needed.
 
 Migrating from 1.5.1 to 1.6.0
 =============================

roundup/backends/back_mysql.py

@@ -36,7 +36,7 @@
 from roundup import date, hyperdb, password
 from roundup.backends import rdbms_common
 import MySQLdb
-import os, shutil
+import os, shutil, sys
 from MySQLdb.constants import ER
 import logging
 
@@ -54,6 +54,8 @@ def connection_dict(config, dbnamestr=None):
         del d['password']
     if 'port' in d:
         d['port'] = int(d['port'])
+    if sys.version_info[0] > 2:
+        d['charset'] = 'utf8'
     return d
 
 def db_nuke(config):
@@ -90,6 +92,8 @@ def db_create(config):
     conn = MySQLdb.connect(**kwargs)
     cursor = conn.cursor()
     command = "CREATE DATABASE %s"%config.RDBMS_NAME
+    if sys.version_info[0] > 2:
+        command += ' CHARACTER SET utf8'
     logging.info(command)
     cursor.execute(command)
     conn.commit()