Running unblob twice is a bit too silent

[e3krisztian]

Describe the bug
When the output directory exists (unblob is called twice), it will exit without any output, except: there is a quick flash.
The exit code will be 1.

To Reproduce
Steps to reproduce the behavior:

1. Run unblob some.zip twice
2. The second run will be very quick, and the output will be empty

Expected behavior
The second output should say, that something is wrong.
When run in verbose mode (unblob some.zip -v), the last line is approximately

... [error    ] Skipped: extraction directory exists extract_dir=some.zip_extract pid=...