debug error message due to cache in logs

[D1sk1n]

This message or similar appears in most logs although cache appears to function properly.

127.0.0.1 - - [02/Jul/2019 19:32:15] "GET /assets/fonts/fontawesome-webfont.woff2?v=4.7.0 HTTP/1.0" 200 -
Exception possibly due to cache backend.
Traceback (most recent call last):
File "/home/ubuntu/.local/lib/python3.6/site-packages/flask_caching/init.py", line 421, in decorated_function
timeout=decorated_function.cache_timeout,
File "/home/ubuntu/.local/lib/python3.6/site-packages/flask_caching/backends/simple.py", line 65, in set
pickle.dumps(value, pickle.HIGHEST_PROTOCOL),
TypeError: cannot serialize '_io.BufferedReader' object