DROP USER looks for sessions by the do-be-dropped user and if found:
* fails with ER_CANNOT_USER in Oracle mode
* continues with ER_ACTIVE_CONNECTIONS_FOR_USER_TO_DROP warning otherwise
Every user being dropped is marked with flag that disallow establishing
a new connections on behalf this user.
MTR .result files currently do not contain output to indicate if a
change_user command has been executed in the corresponding .test files.
Record change_user command in the following format in MTR output only if
disable_query_log is set to false: change_user <user>,<password>,<db>;
All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer Amazon Web
Services, Inc.
when a definer for SP/view is wrong - it shold be ER_MALFORMED_DEFINER,
not ER_NO_SUCH_USER
when one uses current_role as a definer or grantee but there's no
current role - it should be ER_INVALID_ROLE not ER_MALFORMED_DEFINER
when a non-existent user is specified - it should be ER_NO_SUCH_USER,
which should say "The user does not exist", not "Definer does not exist"
clarify ER_CANT_CHANGE_TX_CHARACTERISTICS to say what cannot be changed
