cleanup log message when a non-managed option is passed to mysqldump

A set of mysqldump options are scanned by holland and some basic
safety checks enforced. e.g. flush-privileges isn't supported on mysql 4.1
and dump-events is not supported on 5.0, etc.  When a user passes an explicit
option via additional-options that the mysqldump plugin does not recognize
we flag this as either an 'unparseable option' - which may cause mysqldump to
fail or as a 'user supplied option' - if it looks valid but holland doesn't
have any special check for it.

plugins/holland.backup.mysqldump/holland/backup/mysqldump/command.py

@@ -47,12 +47,12 @@ def check_option(self, option):
         try:
             option, arg = self.OPTION_ARG_CRE.search(option).groups()
         except AttributeError:
-            raise MyOptionError("Unsupported option %r" % option)
+            raise MyOptionError("Unparseable option '%s'" % option)
 
         option = option.replace('_', '-')
 
         if option not in self._options:
-            raise MyOptionError("Unsupported option %r" % option)
+            raise MyOptionError("User supplied option '%s'" % option)
         my_option = self._options[option]
         my_option.check(self.version, arg)