use only Python 3 during the build to complete the migration

configure.ac

@@ -26,33 +26,12 @@ PKG_PROG_PKG_CONFIG
 PKG_CHECK_MODULES(CAJA, libcaja-extension >= $CAJA_REQUIRED)
 PKG_CHECK_MODULES(GLIB, glib-2.0 >= $GLIB_REQUIRED)
 
-AC_PATH_PROG([PYTHON], [python])
 AC_PATH_PROG([PYTHON3], [python3])
 
-AC_PATH_PROG([RST2MAN], [rst2man], [python rst2man.py])
+AC_PATH_PROG([RST2MAN], [rst2man], [python3 rst2man.py])
 AC_SUBST(RST2MAN)
 
 # define module checking macro
-AC_DEFUN([PYTHON_CHECK_MODULE], [
-AC_MSG_CHECKING([for $1])
-
-cat <<EOF | python
-try:
- import $2
-except:
- exit(1)
-else:
- exit(0)
-EOF
-
-if test $? -ne 0; then
-   AC_MSG_RESULT([no])
-   AC_MSG_ERROR([couldn't find $1])
-else
-   AC_MSG_RESULT([yes])
-fi
-])
-
 AC_DEFUN([PYTHON3_CHECK_MODULE], [
 AC_MSG_CHECKING([for $1 on python3])
 
@@ -73,8 +52,7 @@ else
 fi
 ])
 
-PYTHON_CHECK_MODULE(docutils, docutils)
-
+PYTHON3_CHECK_MODULE(docutils, docutils)
 PYTHON3_CHECK_MODULE(gi, gi)
 
 # Make dependency CFLAGS and LIBS available