Handle newly added fields on error response

[Go HAGIWARA / 萩原 豪]

Handling Errors introduces some new fields along with the old ones. These should be treated properly when stringified form of error representation is constructed at below:

p5-Facebook-OpenGraph/lib/Facebook/OpenGraph/Response.pm

Lines 92 to 122 in 8dbc3b5

 sub error_string { 
     my $self = shift; 
  
     # When error occurs, response should be given in a form of below: 
     #{ 
     #  "error": { 
     #    "message": "Message describing the error", 
     #    "type": "OAuthException", 
     #    "code": 190 , 
     #    "error_subcode": 460 
     #  } 
     #} 
     my $error = eval { $self->as_hashref->{error}; }; 
  
     my $err_str = q{}; 
     if ($@ || !$error) { 
         $err_str = $self->message; 
     } 
     else { 
         # sometimes error_subcode is not given 
         $err_str = sprintf( 
                         '%s:%s %s:%s', 
                         $error->{code}, 
                         $error->{error_subcode} || '-', 
                         $error->{type}, 
                         $error->{message}, 
                    ); 
     } 
  
     return $err_str; 
 } 

[Go HAGIWARA / 萩原 豪]

NOTE: This was introduced in v2.1 as below:

In some cases (such as access token invalidation or expiry) the API now returns user-displayable error messages which describe the error and what the person may need to do to resolve it. These error messages will be returned in US English by default, but if you query the Graph API specifying the locale parameter (e.g. ?locale=es_ES) the string may be returned in the specified language.

The above description suggests these fields are not mandatory.