Traceback (most recent call last):
  File "/usr/lib/python3.5/py_compile.py", line 125, in compile
    _optimize=optimize)
  File "<frozen importlib._bootstrap_external>", line 735, in source_to_code
  File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
  File "/in/foo.py", line 25
    outfile.write(f"{fail_count}\n")
                                  ^
SyntaxError: invalid syntax

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.5/py_compile.py", line 129, in compile
    raise py_exc
py_compile.PyCompileError:   File "/in/foo.py", line 25
    outfile.write(f"{fail_count}\n")
                                  ^
SyntaxError: invalid syntax