libpq: Some message style normalization

src/interfaces/libpq/fe-cancel.c

@@ -73,13 +73,13 @@ PQcancelCreate(PGconn *conn)
 	/* Check we have an open connection */
 	if (!conn)
 	{
-		libpq_append_conn_error(cancelConn, "passed connection was NULL");
+		libpq_append_conn_error(cancelConn, "connection pointer is NULL");
 		return (PGcancelConn *) cancelConn;
 	}
 
 	if (conn->sock == PGINVALID_SOCKET)
 	{
-		libpq_append_conn_error(cancelConn, "passed connection is not open");
+		libpq_append_conn_error(cancelConn, "connection not open");
 		return (PGcancelConn *) cancelConn;
 	}
 
@@ -260,7 +260,7 @@ PQcancelPoll(PGcancelConn *cancelConn)
 	 */
 	if (n > 0)
 	{
-		libpq_append_conn_error(conn, "received unexpected response from server");
+		libpq_append_conn_error(conn, "unexpected response from server");
 		conn->status = CONNECTION_BAD;
 		return PGRES_POLLING_FAILED;
 	}

src/interfaces/libpq/fe-connect.c

@@ -1602,8 +1602,8 @@ pqConnectOptions2(PGconn *conn)
 		if (conn->sslnegotiation[0] != 'p')
 		{
 			conn->status = CONNECTION_BAD;
-			libpq_append_conn_error(conn, "sslnegotiation value \"%s\" invalid when SSL support is not compiled in",
-									conn->sslnegotiation);
+			libpq_append_conn_error(conn, "%s value \"%s\" invalid when SSL support is not compiled in",
+									"sslnegotiation", conn->sslnegotiation);
 			return false;
 		}
 #endif

src/interfaces/libpq/fe-exec.c

@@ -2627,7 +2627,7 @@ PQsendTypedCommand(PGconn *conn, char command, char type, const char *target)
 	}
 	else
 	{
-		libpq_append_conn_error(conn, "unknown command type provided");
+		libpq_append_conn_error(conn, "unrecognized message type \"%c\"", command);
 		goto sendFailed;
 	}