windows mysqldump not available

[paaacman]

Hello, thanks for your work.

It may be great to check if mysqldump is available and put an error message if needed.

Currently, without mysqldump (on windows) callable from the command line, here are the logs :

[2016-11-28 14:55:05] app.INFO: [dizda-backup] Dumping MySQL database [] []
[2016-11-28 14:55:32] app.INFO: [dizda-backup] Dumping MySQL database [] []
[2016-11-28 14:55:39] app.CRITICAL: [dizda-backup] Unexpected exception. []
[2016-11-28 14:55:39] app.INFO: [dizda-backup] Cleaning up after us. [] []