Improve error message text

Author: Ekaterina Sokolova

README.md

@@ -407,14 +407,14 @@ postgres=# SELECT pid FROM pg_stat_activity where query like 'delete%';
 (1 row)
 
 postgres=# SELECT pg_progress_bar(23877);
-INFO:  Counting Progress doesn't available
+INFO:  could not get query execution progress
  pg_progress_bar
 -----------------
               -1
 (1 row)
 
 postgres=# SELECT pg_progress_bar_visual(23877, 5);
-INFO:  Counting Progress doesn't available
+INFO:  could not get query execution progress
  pg_progress_bar_visual
 ------------------------
                       -1

pg_query_state.c

@@ -1484,7 +1484,7 @@ pg_progress_bar(PG_FUNCTION_ARGS)
 		progress = GetCurrentNumericState(msg);
 		if (progress < 0)
 		{
-			elog(INFO, "Counting Progress doesn't available");
+			elog(INFO, "could not get query execution progress");
 			PG_RETURN_FLOAT8((float8) -1);
 		}
 		else
@@ -1502,7 +1502,7 @@ pg_progress_bar(PG_FUNCTION_ARGS)
 			}
 			else if (progress < 0)
 			{
-				elog(INFO, "Counting Progress doesn't available");
+				elog(INFO, "could not get query execution progress");
 				break;
 			}