Catch exception when Yara binary is not available for workers

[xdanx]

Subject of the issue

Add a try/catch block when trying to execute the Yara binary

Steps to reproduce

Point yara to an invalid location in the worker config file

Expected behavior

Worker should error out saying Yara binary not available

Actual behavior

Worker raises exception wtih OSError: [Errno 2] No such file or directory which is not so intuivite

[xdanx]

Hello. Fixed in 383af5e1dd9aeb947b5b5e4e0b17d5bb8baa35e8. Will test