tests: write skip explanation from perl scripts also to outer stderr

* tests/CuSkip.pm (skip): New file/module/function, to help
the perl test scripts "skip" a test consistently, emitting
a diagnostic both into the log file and into the outermost
stderr stream that is more likely to be seen by a human.
* tests/check.mk (TESTS_ENVIRONMENT): Add -MCuSkip.
* tests/misc/date-next-dow: Use CuSkip::skip in place of warn+exit-77.
* tests/misc/tty-eof: Likewise.
* tests/misc/uniq: Likewise.
* tests/rm/fail-eperm: Likewise.
* tests/misc/md5sum-newline: Likewise.  Also, s/program_name/ME/.
* tests/misc/ls-misc (setuid_setup, main): Likewise.
* tests/misc/pwd-long: Likewise, and add -I"$abs_srcdir" -MCuSkip
to the $PERL invocation command.
Inspired by a request from Bruno Haible regarding misc/tty-eof:
http://debbugs.gnu.org/8570

1 files changed, 3 insertions, 3 deletions

diff --git a/tests/misc/md5sum-newline b/tests/misc/md5sum-newline
index 3b6d2f46a..efd9fd3a1 100755
--- a/tests/misc/md5sum-newline
+++ b/tests/misc/md5sum-newline
@@ -18,7 +18,7 @@
 
 use strict;
 
-(my $program_name = $0) =~ s|.*/||;
+(my $ME = $0) =~ s|.*/||;
 
 # Turn off localization of executable's output.
 @ENV{qw(LANGUAGE LANG LC_ALL)} = ('C') x 3;
@@ -26,7 +26,7 @@ use strict;
 # See if we can create a file name that contains a newline.
 # Use system, since Perl doesn't let you do this with "open".
 system ('touch', "a\nb") == 0
-  or (warn "$0: failed to create newline-containing file name\n"), exit 77;
+  or CuSkip::skip "$ME: failed to create newline-containing file name\n";
 
 my $degenerate = "d41d8cd98f00b204e9800998ecf8427e";
 my $t = '--text';
@@ -40,5 +40,5 @@ my $save_temps = $ENV{DEBUG};
 my $verbose = $ENV{VERBOSE};
 
 my $prog = 'md5sum';
-my $fail = run_tests ($program_name, $prog, \@Tests, $save_temps, $verbose);
+my $fail = run_tests ($ME, $prog, \@Tests, $save_temps, $verbose);
 exit $fail;