perlcritic_tap: properly fail if provided file can't be read
perlcritic_tap: properly fail if provided file can't be read

Make behavior consistent with the other tap scripts.
Otherwise we'll report a failing test instead of exiting early:

|  % tap/perlcritic_tap /doesnotexist
|  1..26
|  not ok 1        No such file or directory: '/doesnotexist'
|  not ok 2        Usage:
|  not ok 3              perlcritic [-12345 | --brutal | --cruel | --harsh | --stern | --gentle]
|  not ok 4                         [--severity number | name] [{-p | --profile} file | --noprofile]
|  not ok 5                         [--top [ number ]] [--theme expression] [--include pattern]
|  not ok 6                         [--exclude pattern] [{-s | --single-policy} pattern]
|  not ok 7                         [--only | --noonly] [--profile-strictness {warn|fatal|quiet}]
|  [...]

Development sponsored by Sipwise GmbH, recorded as
TT#29615 in customers' ticket system.

hashar/jenkins-debian-glue,hashar/jenkins-debian-glue,mika/jenkins-debian-glue,linuxmaniac/jenkins-debian-glue,linuxmaniac/jenkins-debian-glue,mika/jenkins-debian-glue