improved error message when client cert return failure

lib/ssluse.c

@@ -277,12 +277,15 @@ int cert_stuff(struct connectdata *conn,
 
     file_type = do_file_type(cert_type);
 
+#define SSL_CLIENT_CERT_ERR \
+    "unable to use client certificate (no key found or wrong pass phrase?)"
+
     switch(file_type) {
     case SSL_FILETYPE_PEM:
       /* SSL_CTX_use_certificate_chain_file() only works on PEM files */
       if(SSL_CTX_use_certificate_chain_file(ctx,
                                             cert_file) != 1) {
-        failf(data, "unable to set certificate file (wrong password?)");
+        failf(data, SSL_CLIENT_CERT_ERR);
         return 0;
       }
       break;
@@ -294,7 +297,7 @@ int cert_stuff(struct connectdata *conn,
       if(SSL_CTX_use_certificate_file(ctx,
                                       cert_file,
                                       file_type) != 1) {
-        failf(data, "unable to set certificate file (wrong password?)");
+        failf(data, SSL_CLIENT_CERT_ERR);
         return 0;
       }
       break;