Ensure logging of errors.

The first error of a batch was lost somewhere in the recent changes. My
current best guess is that the rewrite of the copy-batch function made
the handler-bind form setup by the handling-pgsql-notices macro
ineffective, but I can't see why that is.

See #85.

src/pgsql/pgsql.lisp

@@ -84,7 +84,9 @@
 
               ;; normal behavior, on-error-stop being nil
               ;; clean the current transaction before retrying new ones
-              (retry-batch table columns batch batch-rows condition)))
+              (progn
+                (log-message :error "~a" condition)
+                (retry-batch table columns batch batch-rows condition))))
 
         (condition (c)
           ;; non retryable failures