Fix missing __init__.py (OpenAPITools#1933)

Author: Jyhess

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonAiohttpConnexionServerCodegen.java

@@ -45,5 +45,6 @@ public String getName() {
     protected void addSupportingFiles() {
         supportingFiles.add(new SupportingFile("conftest.mustache", testPackage, "conftest.py"));
         supportingFiles.add(new SupportingFile("__init__test.mustache", testPackage, "__init__.py"));
+        supportingFiles.add(new SupportingFile("__init__main.mustache", packageName, "__init__.py"));
     }
 }

samples/server/petstore/python-aiohttp/openapi_server/__init__.py

@@ -0,0 +1,12 @@
+import os
+import connexion
+
+
+def main():
+    options = {
+        "swagger_ui": True
+        }
+    specification_dir = os.path.join(os.path.dirname(__file__), 'openapi')
+    app = connexion.AioHttpApp(__name__, specification_dir=specification_dir, options=options)
+    app.add_api('openapi.yaml', arguments={'title': 'OpenAPI Petstore'}, pass_context_arg_name='request')
+    app.run(port=8080)