add dep test error logging

Author: wchristian

xt/dependent-modules.t

@@ -5,5 +5,16 @@ use Test::DependentModules 'test_all_dependents';
 
 skip_all "ENV var TEST_DEPENDENTS not set" if not $ENV{TEST_DEPENDENTS};
 
+# duplicate error output into an array for later printing
+my @error_log;
+my $old = \&Test::DependentModules::_error_log;
+my $new = sub { push @error_log, @_; $old->(@_); };
+{ no warnings 'redefine'; *Test::DependentModules::_error_log = $new; }
+
 test_all_dependents    #
   PPI => { exclude => qr/^(Apache2-SSI|Devel-IPerl|Padre)$/ };
+
+diag "\n\n---------- ERROR LOG START -----------\n\n",
+  @error_log,
+  "\n\n---------- ERROR LOG END -----------\n\n";
+done_testing;