wrapper: fail properly with unsupported versions of Subvertpy (fixes #212) Calling subvertpy.wc.api_version() will raise an AttributeError with versions of Subvertpy prior to 0.7.4. This AttributeError completely breaks hgsubversion, as our infrastructure assumes that only ImportErrors are raised during imports. Delaying the call to api_version() until after the Subvertpy version check should make things work again.