Add None term_to_binary conversion to an undefined Erlang atom.

Author: okeuday

erlang.py

@@ -599,6 +599,8 @@ def _term_to_binary(term):
         return _dict_to_binary(term)
     elif type(term) == bool:
         return OtpErlangAtom(term and b'true' or b'false').binary()
+    elif term is None:
+        return OtpErlangAtom(b'undefined').binary()
     elif isinstance(term, OtpErlangAtom):
         return term.binary()
     elif isinstance(term, OtpErlangList):

tests/erlang_tests.py

@@ -434,9 +434,10 @@ def test_term_to_binary_string_basic(self):
     def test_term_to_binary_string(self):
         self.assertEqual(b'\x83j', erlang.term_to_binary(''))
         self.assertEqual(b'\x83k\0\4test', erlang.term_to_binary('test'))
-    def test_term_to_binary_boolean(self):
+    def test_term_to_binary_predefined_atom(self):
         self.assertEqual(b'\x83s\4true', erlang.term_to_binary(True))
         self.assertEqual(b'\x83s\5false', erlang.term_to_binary(False))
+        self.assertEqual(b'\x83s\x09undefined', erlang.term_to_binary(None))
     def test_term_to_binary_short_integer(self):
         self.assertEqual(b'\x83a\0', erlang.term_to_binary(0))
         self.assertEqual(b'\x83a\xff', erlang.term_to_binary(255))