Log subject common name also.

May help understanding problems.

GpgMELogger.h

@@ -13,6 +13,8 @@
 #include <Wt/WLogger.h>
 #include <Wt/WApplication.h>
 #include <Wt/WEnvironment.h>
+#include <Wt/WSslCertificate.h>
+#include <Wt/WSslInfo.h>
 #include <gpgme++/error.h>
 #include <mutex>
 
@@ -26,10 +28,26 @@ static void LogGpgMEError(const GpgME::Error& e)
     if (e.code() == 0)
         return;
     std::unique_lock<std::mutex> lock(gs_logGpgMEError);
+
+    const vector<WSslCertificate::DnAttribute> * dnAttr
+            = &(WApplication::instance()->environment().sslInfo()
+            ->clientCertificate().subjectDn());
+    WString subjectCommonName = WString::Empty;
+    for (uint i = 0; i < dnAttr->size(); i++)
+    {
+        if (dnAttr->at(i).name() == WSslCertificate::DnAttributeName::CommonName)
+        {
+            subjectCommonName = dnAttr->at(i).value();
+            break;
+        }
+    }
+    
+
     const string logfile = WApplication::appRoot() + string("gpgme.log");
     WLogger logger;
     logger.setFile(logfile);
     logger.entry("") << WLogger::timestamp
+            << WLogger::sep << subjectCommonName
             << WLogger::sep << WApplication::instance()->environment().userAgent()
             << WLogger::sep << std::to_string(e.code())
             << WLogger::sep << e.asString();