Add async flag when wrapping async function (#111)

[soldag]

Python 3.11 uses inspect.iscoroutinefunction to determine whether a test needs to be awaited or not. Since the wrapper created by ddt doesn't have the async code flag, iscoroutinefunction returns False and it is not awaited causing the issue described in #111.

I added a simple fix by adding the async code flag to the wrapper if the original function is a coroutine function.

[soldag]

@wswld Any chance you can have a look at this? It currently block me from using ddt in my project and it's a simple fix.

[wswld]

@soldag hi, sorry for the wait.
Could you please try pinning Ubuntu version as was done here?
Hopefully that will resolve the 3.6/2.7 issue we're having

PS: Please mention me if any updates otherwise I'm not notified

[wswld]

@soldag never mind, I've updated the versions
Now tests run, but there is an issue with Python 3.7
Could you please look into it?

[soldag]

@wswld Thanks for looking into it. I forgot that IsolatedAsyncioTestCase was only introduced in python 3.8. I changed it to use aiounittest.AsyncTestCase. Hope that's fine for you.

[wswld]

@soldag looks good now, thanks