libpq: Fix up some error message coding

This applies the new error message API from commit 0873b2d354 to the
changes introduced by bbf9c282ce.  The latter was committed shortly
after the former, so it probably didn't get the news in time.

src/interfaces/libpq/fe-protocol3.c

@@ -1420,20 +1420,21 @@ pqGetNegotiateProtocolVersion3(PGconn *conn)
 	}
 
 	if (their_version < conn->pversion)
-		appendPQExpBuffer(&conn->errorMessage,
-						  libpq_gettext("protocol version not supported by server: client uses %u.%u, server supports up to %u.%u\n"),
-						  PG_PROTOCOL_MAJOR(conn->pversion), PG_PROTOCOL_MINOR(conn->pversion),
-						  PG_PROTOCOL_MAJOR(their_version), PG_PROTOCOL_MINOR(their_version));
+		libpq_append_conn_error(conn, "protocol version not supported by server: client uses %u.%u, server supports up to %u.%u",
+								PG_PROTOCOL_MAJOR(conn->pversion), PG_PROTOCOL_MINOR(conn->pversion),
+								PG_PROTOCOL_MAJOR(their_version), PG_PROTOCOL_MINOR(their_version));
 	if (num > 0)
+	{
 		appendPQExpBuffer(&conn->errorMessage,
-						  libpq_ngettext("protocol extension not supported by server: %s\n",
-										 "protocol extensions not supported by server: %s\n", num),
+						  libpq_ngettext("protocol extension not supported by server: %s",
+										 "protocol extensions not supported by server: %s", num),
 						  buf.data);
+		appendPQExpBufferChar(&conn->errorMessage, '\n');
+	}
 
 	/* neither -- server shouldn't have sent it */
 	if (!(their_version < conn->pversion) && !(num > 0))
-		appendPQExpBuffer(&conn->errorMessage,
-						  libpq_gettext("invalid %s message"), "NegotiateProtocolVersion");
+		libpq_append_conn_error(conn, "invalid %s message", "NegotiateProtocolVersion");
 
 	termPQExpBuffer(&buf);
 	return 0;