Fix for

Bug#37492 timing bug in subselect.test
+ similar weaknesses found during testing
+ replace error numbers by error names

mysql-test/include/wait_condition.inc

+# include/wait_condition.inc
+#
+# SUMMARY
+#
+#    Waits until the passed statement returns true, or the operation
+#    times out.
+#
+# USAGE
+#
+#    let $wait_condition=
+#      SELECT c = 3 FROM t;
+#    --source include/wait_condition.inc
+#
+#   OR
+#
+#    let $wait_timeout= 60; # Override default 30 seconds with 60.
+#    let $wait_condition=
+#      SELECT c = 3 FROM t;
+#    --source include/wait_condition.inc
+#    --echo Executed the test condition $wait_condition_reps times
+#
+# EXAMPLE
+#    events_bugs.test, events_time_zone.test
+#
+
+--disable_query_log
+
+let $wait_counter= 300;
+if ($wait_timeout)
+{
+  let $wait_counter= `SELECT $wait_timeout * 10`;
+}
+# Reset $wait_timeout so that its value won't be used on subsequent
+# calls, and default will be used instead.
+let $wait_timeout= 0;
+
+# Keep track of how many times the wait condition is tested
+# This is used by some tests (e.g., main.status)
+let $wait_condition_reps= 0;
+while ($wait_counter)
+{
+    let $success= `$wait_condition`;
+    inc $wait_condition_reps;
+    if ($success)
+    {
+        let $wait_counter= 0;
+    }
+    if (!$success)
+    {
+        real_sleep 0.1;
+        dec $wait_counter;
+    }
+}
+if (!$success)
+{
+  echo Timeout in wait_condition.inc for $wait_condition;
+}
+
+--enable_query_log