One of the regexes has a bogus \o instead of plain 'o'. Somehow this magically worked on all versions of python, until 3.6 came along and complained Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- generator.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Pushed as a trival fix / python 3.6 build fix diff --git a/generator.py b/generator.py index 730e456..2c3b667 100755 --- a/generator.py +++ b/generator.py @@ -1091,7 +1091,7 @@ def is_integral_type (name): return not re.search ("^(unsigned)? ?(int|long)$", name) is None def is_optional_arg(info): - return re.search("^\(?\optional\)?", info) is not None + return re.search("^\(?optional\)?", info) is not None # Functions returning lists which need special rules to check for errors # and raise exceptions. functions_list_exception_test = { -- 2.9.3