Troposphere library "AttributeError" fix and python3.9 runtime support

zappa/__init__.py

@@ -1,6 +1,6 @@
 import sys
 
-SUPPORTED_VERSIONS = [(3, 6), (3, 7), (3, 8)]
+SUPPORTED_VERSIONS = [(3, 6), (3, 7), (3, 8), (3, 9)]
 
 if sys.version_info[:2] not in SUPPORTED_VERSIONS:
     formatted_supported_versions = [

zappa/core.py

@@ -2414,7 +2414,7 @@ def create_stack_template(
 
         # build a fresh template
         self.cf_template = troposphere.Template()
-        self.cf_template.add_description("Automatically generated with Zappa")
+        self.cf_template.set_description("Automatically generated with Zappa")
         self.cf_api_resources = []
         self.cf_parameters = {}