Fix for PR automake/398: * m4/python.m4: Do not call AC_PATH_PROGS if $PYTHON is already set. Display `none' instead of `:' and $PYTHON is set to `:' when no suitable interpreter is found. Honor ACTION-IF-FOUND and ACTION-IF-NOT-FOUND. * automake.texi (Python): Document ACTION-IF-FOUND and ACTION-IF-NOT-FOUND. * tests/python4.test, tests/python5.test, tests/python6.test, tests/python7.test, tests/python8.test, tests/python9.test: New files. * tests/Makefile.am (TESTS): Add them. Report from Per Cederqvist.