added several error messages for better error tracking

db/db_ctx.c

@@ -233,6 +233,7 @@ int db_add_db(db_ctx_t* ctx, const char* uri)
 
  error:
 	if (parsed_uri) db_uri_free(parsed_uri);
+	ERR("db: db_add_db failed\n");
 	return -1;
 }
 

db/db_drv.c

@@ -94,7 +94,10 @@ int db_drv_call(str* module, char* func_name, void* db_struct, int offset)
 	int ret;
 
 	ret = db_drv_func(&func, module, func_name);
-	if (ret < 0) return -1;
+	if (ret < 0) {
+		ERR("db: db_drv_call failed\n");
+		return -1;
+	}
 
 	if (ret == 0) {
 		db_payload_idx = offset;

db/db_fld.c

@@ -115,6 +115,7 @@ db_fld_t* db_fld_copy(db_fld_t* fld)
 	return newp;
 
  error:
+ 	ERR("db_fld_copy() failed\n");
 	if (newp) {
 		db_gen_free(&newp->gen);
 		pkg_free(newp);