fix aiohttp error handling (#364)

* fix aiohttp error handling

* fix coegen

* fix codedgen of async/await error handling and json response

* Bump black from 21.10b0 to 21.12b0 (#365)

Bumps [black](https://github.com/psf/black) from 21.10b0 to 21.12b0.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/main/CHANGES.md)
- [Commits](https://github.com/psf/black/commits)

---
updated-dependencies:
- dependency-name: black
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

* Fix: RST document format error (#357)

* fix: rst format

* fix aiohttp error handling

* fix conflict

* fix codedgen of async/await error handling and json response

* add async_api some test

* add exeptions test case

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: NiJia Lin <nijia.lin@linecorp.com>

Author: 3 people

linebot/aiohttp_async_http_client.py

@@ -147,9 +147,9 @@ async def content(self):
         return await self.response.content.read()
 
     @property
-    def json(self):
+    async def json(self):
         """Get response body as json-decoded."""
-        return self.response.json()
+        return await self.response.json()
 
     def iter_content(self, chunk_size=1024):
         """Get response body as iterator content (stream).