Bug 8818: make sure we load modules before using them

An eval { eval "require $module;" }; was replaced with
eval { eval { require $module; }; }; which is a no-op, meaning that
the linker was not getting loaded, and the catalog module was throwing
up a big nasty error every time someone tried to save a record with a
heading. This patch replaces the require with can_load from
Module::Load::Conditional, which is PBP-friendly, and offers equivalent
functionality.

Signed-off-by: Nicole C. Engard <nengard@bywatersolutions.com>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>

C4/Biblio.pm

@@ -28,6 +28,7 @@ use MARC::Record;
 use MARC::File::USMARC;
 use MARC::File::XML;
 use POSIX qw(strftime);
+use Module::Load::Conditional qw(can_load);
 
 use C4::Koha;
 use C4::Dates qw/format_date/;
@@ -491,13 +492,11 @@ sub BiblioAutoLink {
 
     my $linker_module =
       "C4::Linker::" . ( C4::Context->preference("LinkerModule") || 'Default' );
-    eval { eval {require $linker_module}; };
-    if ($@) {
+    unless ( can_load( modules => { $linker_module => undef } ) ) {
         $linker_module = 'C4::Linker::Default';
-        eval {require $linker_module};
-    }
-    if ($@) {
-        return 0, 0;
+        unless ( can_load( modules => { $linker_module => undef } ) ) {
+            return 0, 0;
+        }
     }
 
     my $linker = $linker_module->new(

misc/link_bibs_to_authorities.pl

@@ -18,6 +18,7 @@ use Pod::Usage;
 use Data::Dumper;
 use Time::HiRes qw/time/;
 use POSIX qw/strftime ceil/;
+use Module::Load::Conditional qw(can_load);
 
 sub usage {
     pod2usage( -verbose => 2 );
@@ -53,13 +54,11 @@ if ( not $result or $want_help ) {
 
 my $linker_module =
   "C4::Linker::" . ( C4::Context->preference("LinkerModule") || 'Default' );
-eval { eval "require $linker_module"; };
-if ($@) {
+unless ( can_load( modules => { $linker_module => undef } ) ) {
     $linker_module = 'C4::Linker::Default';
-    eval "require $linker_module";
-}
-if ($@) {
-    die "Unable to load linker module. Aborting.";
+    unless ( can_load( modules => { $linker_module => undef } ) ) {
+        die "Unable to load linker module. Aborting.";
+    }
 }
 
 my $linker = $linker_module->new(