Regression issue: _gdbm.error: [Errno 11] Resource temporarily unavailable

[dvarounis]

The plugin frequently returns _gdbm.error: [Errno 11] Resource temporarily unavailable under high load.
Probably need to optimize shelve.open() usage (https://docs.python.org/3.6/library/shelve.html)

[noamzilo]

I am getting this error every time I try to use shelve in parallel such as

1. pytest ultiple tests
2. on import time, when opening caches as class variables