error: add error_setg_file_open() helper

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Acked-by: Kevin Wolf <kwolf@redhat.com>

include/qapi/error.h

@@ -44,6 +44,11 @@ void error_set_errno(Error **err, int os_error, ErrorClass err_class, const char
 #define error_setg_errno(err, os_error, fmt, ...) \
     error_set_errno(err, os_error, ERROR_CLASS_GENERIC_ERROR, fmt, ## __VA_ARGS__)
 
+/**
+ * Helper for open() errors
+ */
+void error_setg_file_open(Error **errp, int os_errno, const char *filename);
+
 /**
  * Returns true if an indirect pointer to an error is pointing to a valid
  * error object.

util/error.c

@@ -71,6 +71,11 @@ void error_set_errno(Error **errp, int os_errno, ErrorClass err_class,
     *errp = err;
 }
 
+void error_setg_file_open(Error **errp, int os_errno, const char *filename)
+{
+    error_setg_errno(errp, os_errno, "Could not open '%s'", filename);
+}
+
 Error *error_copy(const Error *err)
 {
     Error *err_new;