Fix hstore_plpython test when python3 is used.

Due to b67aaf21 / CREATE EXTENSION ... CASCADE the test output
contains the extension name in yet another place. Since that's variable
depending on the python version...

Add yet another name mangling stanza to regress-python3-mangle.mk.

Author: Petr Jelinek

src/pl/plpython/regress-python3-mangle.mk

@@ -25,6 +25,7 @@ pgregress-python3-mangle:
 	      -e "s/LANGUAGE plpython2u/LANGUAGE plpython3u/g" \
 	      -e "s/EXTENSION \([^ ]*_\)*plpythonu/EXTENSION \1plpython3u/g" \
 	      -e "s/EXTENSION \([^ ]*_\)*plpython2u/EXTENSION \1plpython3u/g" \
+	      -e 's/installing required extension "plpython2u"/installing required extension "plpython3u"/g' \
 	    $$file >`echo $$file | sed 's,^.*/\([^/][^/]*/\)\([^/][^/]*\)$$,\1python3/\2,'` || exit; \
 	done