print errors in pkey utility

Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2177)

apps/pkey.c

@@ -179,6 +179,8 @@ int pkey_main(int argc, char **argv)
     ret = 0;
 
  end:
+    if (ret != 0)
+        ERR_print_errors(bio_err);
     EVP_PKEY_free(pkey);
     release_engine(e);
     BIO_free_all(out);