[python-asyncio] tests and fixes (#7235)

* fix: creating ssl context and passing args/files/forms

* feat: python-async add tests

* chore: rebuild petstore sample for python, tornado and asyncio

* feat: add python asyncio to travis

* feat: print coverage (python-asyncio)

samples/client/petstore/python-asyncio/Makefile

@@ -0,0 +1,18 @@
+ #!/bin/bash
+
+REQUIREMENTS_FILE=dev-requirements.txt
+REQUIREMENTS_OUT=dev-requirements.txt.log
+SETUP_OUT=*.egg-info
+VENV=.venv
+
+clean:
+		rm -rf $(REQUIREMENTS_OUT)
+		rm -rf $(SETUP_OUT)
+		rm -rf $(VENV)
+		rm -rf .tox
+		rm -rf .coverage
+		find . -name "*.py[oc]" -delete
+		find . -name "__pycache__" -delete
+
+test-all: clean
+		bash ./test_python3.sh