Aiohttp

Running « pip install aiohttp » returns:

```
Collecting aiohttp
Using cached aiohttp-3.7.3.tar.gz (1.1 MB)
Installing build dependencies ... done
Getting requirements to build wheel ... error
ERROR: Command errored out with exit status 1:
command: /private/var/containers/Bundle/Application/01DCC177-B81B-4733-9FEC-7CE29970742E/a-Shell.app/Library/bin/python3 /private/var/containers/Bu
ndle/Application/01DCC177-B81B-4733-9FEC-7CE29970742E/a-Shell.app/Library/lib/python3.9/site-packages/pip/_vendor/pep517/_in_process.py get_requires_f
or_build_wheel /private/var/mobile/Containers/Data/Application/2DA5A700-076C-430A-844D-FBF9D6DAD2CA/tmp/tmpdg4al5ht
cwd: /private/var/mobile/Containers/Data/Application/2DA5A700-076C-430A-844D-FBF9D6DAD2CA/tmp/pip-install-kavvb_0k/aiohttp
Complete output (12 lines):
Traceback (most recent call last):
File "/private/var/containers/Bundle/Application/01DCC177-B81B-4733-9FEC-7CE29970742E/a-Shell.app/Library/lib/python3.9/site-packages/pip/_vendor/
pep517/_in_process.py", line 280, in
main()
File "/private/var/containers/Bundle/Application/01DCC177-B81B-4733-9FEC-7CE29970742E/a-Shell.app/Library/lib/python3.9/site-packages/pip/_vendor/
pep517/_in_process.py", line 263, in main
json_out['return_val'] = hook(**hook_input['kwargs'])
File "/private/var/containers/Bundle/Application/01DCC177-B81B-4733-9FEC-7CE29970742E/a-Shell.app/Library/lib/python3.9/site-packages/pip/_vendor/
pep517/_in_process.py", line 108, in get_requires_for_build_wheel
backend = _build_backend()
File "/private/var/containers/Bundle/Application/01DCC177-B81B-4733-9FEC-7CE29970742E/a-Shell.app/Library/lib/python3.9/site-packages/pip/_vendor/
pep517/_in_process.py", line 83, in _build_backend
ep = os.environ['PEP517_BUILD_BACKEND']
File "/private/var/containers/Bundle/Application/01DCC177-B81B-4733-9FEC-7CE29970742E/a-Shell.app/Library/lib/python3.9/os.py", line 682, in __get
item__
raise KeyError(key) from None
KeyError: 'PEP517_BUILD_BACKEND'
----------------------------------------
ERROR: Command errored out with exit status 1: /private/var/containers/Bundle/Application/01DCC177-B81B-4733-9FEC-7CE29970742E/a-Shell.app/Library/bin
/python3 /private/var/containers/Bundle/Application/01DCC177-B81B-4733-9FEC-7CE29970742E/a-Shell.app/Library/lib/python3.9/site-packages/pip/_vendor/p
ep517/_in_process.py get_requires_for_build_wheel /private/var/mobile/Containers/Data/Application/2DA5A700-076C-430A-844D-FBF9D6DAD2CA/tmp/tmpdg4al5ht
Check the logs for full command output.
```