[build] Fix Python detection in Autotools build.

This was a latent bug: the PYTHON variable was not set in Makefiles,
only PYTHON3 was, but scripts were still invoked with $(PYTHON).

While at it, let's also accept python2 >= 2.7.

diff --git a/configure.ac b/configure.ac
index 32ba148517f59130c3a098c16beb5491fdd973b2..3529a65ec91f6b6796fa24c60d1b5eaf56d7e873 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -59,10 +59,9 @@ dnl Check for stuff needed for building the GiNaC interactive shell (ginsh).
 AC_CHECK_HEADERS(unistd.h)
 GINAC_HAVE_RUSAGE
 GINAC_READLINE
 AC_CHECK_HEADERS(unistd.h)
 GINAC_HAVE_RUSAGE
 GINAC_READLINE

-dnl Python3 is necessary for building function.{cpp,h}
-AC_PATH_PROG(PYTHON3, python3, "")
-AS_IF([test -z "$PYTHON3" -a ! -f "$srcdir/ginac/function.cpp"],
-      [AC_MSG_ERROR([GiNaC will not compile because Python3 is missing])])
+dnl Python is necessary for building function.{cpp,h}
+AM_PATH_PYTHON([2.7],,
+               [AC_MSG_ERROR([GiNaC will not compile because Python is missing])])

 
 dnl Check for dl library (needed for GiNaC::compile).
 GINAC_EXCOMPILER
 
 dnl Check for dl library (needed for GiNaC::compile).
 GINAC_EXCOMPILER