Describe the bug

After upgrading to multidict 4.7.1 we have found that the applications we bundle using PyInstaller crash. Actually, I discovered this problem because we use aiohttp which depends on multidict. Version 4.6.1 does not have this problem.

To Reproduce

1. Create a new virtual environment
2. pip install multidict==4.7.1 pyinstaller
3. Create a simple test.py script with:

print("Hello!")
import multidict

4. Bundle it pyinstaller test.py
5. Run it:

./dist/test/test
Hello!
[1]    22548 segmentation fault (core dumped)  ./dist/test/test

Expected behavior

Application prints "Hello!" and quits nicely.

Logs/tracebacks

Provided above.

Your version of the Python

Observed with 3.6.9 and 3.7.5

Your version of the multidict distribution

4.7.1

Additional context

N/A