Racon failing does not cause Unicycler to fail

[audy]

We recently ran into an issue where Unicycler output would be different depending on if we ran it on a Haswell versus Skylake CPU. The issue turned out to be due to Racon being compiled with AVX-512 instructions which are not supported on a Haswell chip. This issue was especially difficult to diagnose due to there being no messages in the log indicating that Racon crashed.

I went to add a check to the return code for Racon and notice that Unicycler intentionally ignores failed calls to Racon due to sporadic crashing.

Adding an error message to the logs would be helpful but what do you think about specifying a --strict-racon flag that causes Unicycler to fail if Racon does not exit successfully or --min-racon-rounds=n to fail if Racon doesn't run successfully at leastn times?