When debugging uwsgi logging issues with python3.7 i got this on python 3.7.2:
Traceback (most recent call last):
  File "/usr/lib/python3.7/logging/__init__.py", line 269, in _after_at_fork_weak_calls
    _at_fork_weak_calls('release')
  File "/usr/lib/python3.7/logging/__init__.py", line 261, in _at_fork_weak_calls
    method_name, "method:", err, file=sys.stderr)
  File "/usr/lib/python3.7/logging/__init__.py", line 1066, in __repr__
    name = name + ' '
TypeError: unsupported operand type(s) for +: 'int' and 'str'

AFAICS uwsgi creates sys.stderr as an unbuffered file with PyFile_FromFd() and sets it to sys dict.