python: Drop support for Python 2.

Python 2 reached end of life on 2020-01-01:
https://python3statement.org/
https://pythonclock.org/

The minimum version required is now Python 3.4 (since that is the
version in Debian oldoldstable), but 3.6 is the minimum version that
I actually test.

docs/guestfs-building.pod

@@ -307,11 +307,10 @@ Optional.  For testing the common OCaml modules.
 
 Optional.  Used to build and test the Perl bindings.
 
-=item Python E<ge> 2.7
+=item Python E<ge> 3.4
 
-Optional.  Used to build the Python bindings.  For building
-Python 2 or Python 3 bindings, see
-L</BUILDING PYTHON 2 AND PYTHON 3 BINDINGS> below.
+Optional.  Used to build the Python bindings.
+S<Python 2> support was removed in S<libguestfs 1.42.1>.
 
 =item Python C<unittest>
 
@@ -528,8 +527,6 @@ If there is a file in the top build directory called F<localenv>, then
 it will be sourced by C<make>.  This file can contain any local
 environment variables needed, eg. for skipping tests:
 
- # Use an alternate python binary.
- export PYTHON=python3
  # Skip this test, it is broken.
  export SKIP_TEST_BTRFS_FSCK=1
 
@@ -683,8 +680,7 @@ F<appliance/make.sh.in> to understand precisely what this does.
 This environment variable may be set to point to a python binary
 (eg. C<python3>).  When C<./configure> runs, it inspects this python
 binary to find the version of Python, the location of Python libraries
-and so on.  See
-L</BUILDING PYTHON 2 AND PYTHON 3 BINDINGS> below.
+and so on.
 
 =item B<SUPERMIN>
 
@@ -752,23 +748,6 @@ tarball, eg:
 and run the libguestfs programs and virt tools in the normal way,
 eg. using the F<./run> script (see above).
 
-=head1 BUILDING PYTHON 2 AND PYTHON 3 BINDINGS
-
-The F<./configure> script detects the currently installed version of
-Python using whatever program is called C<python> in the current
-C<$PATH>.  Libguestfs will build Python 2 or Python 3 bindings as
-appropriate.
-
-You can override this behaviour by specifying an alternate Python
-binary, eg:
-
- PYTHON=/usr/bin/python3 ./configure
-
-To build parallel Python 2 and Python 3 bindings, you will need to
-build libguestfs twice.  The second time, you can disable all the
-other bindings and tools and just build the Python bindings.  See the
-Fedora spec file (see below) for a complete example of how to do this.
-
 =head1 BUILDING A PACKAGE FOR FEDORA
 
 The Fedora spec file is stored under:

generator/python.ml

@@ -174,13 +174,8 @@ and generate_python_structs () =
             pr "    goto err;\n";
             pr "  PyDict_SetItemString (dict, \"%s\", value);\n" name;
         | name, FBuffer ->
-            pr "#if PY_MAJOR_VERSION >= 3\n";
             pr "  value = PyBytes_FromStringAndSize (%s->%s, %s->%s_len);\n"
               typ name typ name;
-            pr "#else\n";
-            pr "  value = PyString_FromStringAndSize (%s->%s, %s->%s_len);\n"
-              typ name typ name;
-            pr "#endif\n";
             pr "  if (value == NULL)\n";
             pr "    goto err;\n";
             pr "  PyDict_SetItemString (dict, \"%s\", value);\n" name;
@@ -493,11 +488,7 @@ and generate_python_actions actions () =
            pr "  guestfs_int_free_string_list (r);\n";
            pr "  if (py_r == NULL) goto out;\n";
        | RBufferOut _ ->
-           pr "#if PY_MAJOR_VERSION >= 3\n";
            pr "  py_r = PyBytes_FromStringAndSize (r, size);\n";
-           pr "#else\n";
-           pr "  py_r = PyString_FromStringAndSize (r, size);\n";
-           pr "#endif\n";
            pr "  free (r);\n";
            pr "  if (py_r == NULL) goto out;\n";
       );
@@ -575,7 +566,6 @@ and generate_python_module () =
 
   (* Init function. *)
   pr "\
-#if PY_MAJOR_VERSION >= 3
 static struct PyModuleDef moduledef = {
   PyModuleDef_HEAD_INIT,
   \"libguestfsmod\",     /* m_name */
@@ -587,18 +577,13 @@ static struct PyModuleDef moduledef = {
   NULL,                  /* m_clear */
   NULL,                  /* m_free */
 };
-#endif
 
 static PyObject *
 moduleinit (void)
 {
   PyObject *m;
 
-#if PY_MAJOR_VERSION >= 3
   m = PyModule_Create (&moduledef);
-#else
-  m = Py_InitModule ((char *) \"libguestfsmod\", methods);
-#endif
 
   if (m != NULL)
     guestfs_int_py_extend_module (m);
@@ -606,7 +591,6 @@ moduleinit (void)
   return m; /* m might be NULL if module init failed */
 }
 
-#if PY_MAJOR_VERSION >= 3
 extern PyMODINIT_FUNC PyInit_libguestfsmod (void);
 
 PyMODINIT_FUNC
@@ -614,15 +598,6 @@ PyInit_libguestfsmod (void)
 {
   return moduleinit ();
 }
-#else
-extern void initlibguestfsmod (void);
-
-void
-initlibguestfsmod (void)
-{
-  (void) moduleinit ();
-}
-#endif
 "
 
 (* Generate Python module. *)

m4/guestfs-python.m4

@@ -19,27 +19,40 @@ dnl Check for Python (optional, for Python bindings).
 PYTHON_PREFIX=
 PYTHON_VERSION=
 PYTHON_INSTALLDIR=
-PYTHON_REQ_MAJOR=2
-PYTHON_REQ_MINOR=7
 
 AC_ARG_ENABLE([python],
     AS_HELP_STRING([--disable-python], [disable Python language bindings]),
     [],
     [enable_python=yes])
 AS_IF([test "x$enable_python" != "xno"],[
-    AC_CHECK_PROG([PYTHON],[python],[python],[no])
+    AC_CHECK_PROGS([PYTHON],[python3 python],[no])
 
     if test "x$PYTHON" != "xno"; then
 	AC_MSG_CHECKING([Python version])
         PYTHON_VERSION_MAJOR=`$PYTHON -c "import sys; print (sys.version_info@<:@0@:>@)"`
         PYTHON_VERSION_MINOR=`$PYTHON -c "import sys; print (sys.version_info@<:@1@:>@)"`
         PYTHON_VERSION="$PYTHON_VERSION_MAJOR.$PYTHON_VERSION_MINOR"
-        AS_IF([test "$PYTHON_VERSION_MAJOR" -lt $PYTHON_REQ_MAJOR || ( test "$PYTHON_VERSION_MAJOR" -eq $PYTHON_REQ_MAJOR && test "$PYTHON_VERSION_MINOR" -lt $PYTHON_REQ_MINOR )],[
-           AC_MSG_ERROR([found Python $PYTHON_VERSION, while Python $PYTHON_REQ_MAJOR.$PYTHON_REQ_MINOR is required])
+        AS_IF([test -n "$PYTHON_VERSION"],[
+            AC_MSG_RESULT([$PYTHON_VERSION])
+        ],[
+            AC_MSG_NOTICE([Python bindings disabled])
+            enable_python=no
         ])
-	AC_MSG_RESULT([$PYTHON_VERSION])
 
-        # Debian: python-2.7.pc, python-3.2.pc
+        AC_MSG_CHECKING([Python major version is 3])
+        AS_IF([test "x$PYTHON_VERSION_MAJOR" = "x3"],[
+            AC_MSG_RESULT([yes])
+        ],[
+            AC_MSG_RESULT([no])
+            AC_MSG_ERROR([Python $PYTHON_VERSION_MAJOR <> 3 is no longer supported.
+
+Python 2 end of life is 2020-01-01 and libguestfs >= 1.42.1 no longer
+supports it.
+
+If you want to use Python 2, you will need to use libguestfs 1.40 or 1.42.0.])
+        ])
+
+        # Debian: python-3.2.pc
         PKG_CHECK_MODULES([PYTHON], [python-"$PYTHON_VERSION"],[
             have_python_module=1
             AC_SUBST([PYTHON_CFLAGS])

python/handle.c

@@ -384,30 +384,18 @@ guestfs_int_py_put_table (char * const * const argv)
 PyObject *
 guestfs_int_py_fromstring (const char *str)
 {
-#if PY_MAJOR_VERSION < 3
-  return PyString_FromString (str);
-#else
   return PyUnicode_FromString (str);
-#endif
 }
 
 PyObject *
 guestfs_int_py_fromstringsize (const char *str, size_t size)
 {
-#if PY_MAJOR_VERSION < 3
-  return PyString_FromStringAndSize (str, size);
-#else
   return PyUnicode_FromStringAndSize (str, size);
-#endif
 }
 
 char *
 guestfs_int_py_asstring (PyObject *obj)
 {
-#if PY_MAJOR_VERSION < 3
-  return PyString_AsString (obj);
-#else
   PyObject *bytes = PyUnicode_AsUTF8String (obj);
   return PyBytes_AS_STRING (bytes);
-#endif
 }