Lock-file error-handling - suggest switch to graceful exit

[jmetz]

When lock-file exists, currently https://github.com/VoltaireNoir/blight/blob/main/src/utils.rs#L374-L378 causes a panic:

./blight inc 10 
Error A panic occured
Reason failed to open lock file: Os { code: 13, kind: PermissionDenied, message: "Permission denied" }
Location src/utils.rs:378:10
Tip This is unexpected behavior. Please report this issue at https://github.com/VoltaireNoir/blight/issues
fish: Job 1, './blight inc 10' terminated by signal SIGABRT (Abort)

Most applications with lock-files that I've used tend to exit gracefully, as this kind of thing does happen from time-to-time.

Recommend switching from expect and the resulting panic, to matching the failure and reporting a less panicky message to the user along the lines of eg pacman:

error: failed to init transaction (unable to lock database)
error: could not lock database: File exists
  if you're sure a package manager is not already
  running, you can remove /var/lib/pacman/db.lck

Background

I just installed and ran this on an arch-type system, and probably did something wrong at some point resulting in the stray lock-file.

[VoltaireNoir]

Thank you for reporting the issue. You're right about turning this into a normal error instead of making the program panic. I'll make fix it and cut a new release soon.