CachePath fixed bad cache from __new__ surviving error in __init__

when initing a cache if a NoCachedMetadataError is raised then delete
the _cache attribute from the _local path to avoid wierdness

this manifested as a NameError in data.setter where cmeta could not
be bound the first time, but the stale ref to a non-existent _cache
would cause the second if statement to fire

augpathlib/caches.py

@@ -100,6 +100,7 @@ def __init__(self, *args, meta=None, remote=None, **kwargs):
             self._meta_updater(meta)
         else:
             if self.meta is None:
+                delattr(self._local, '_cache')
                 raise exc.NoCachedMetadataError(self.local)
 
         super().__init__()

augpathlib/core.py

@@ -594,6 +594,7 @@ def data(self):
     def data(self, generator):
         if self.cache is not None:
             cmeta = self.cache.meta
+
         # FIXME do we touch a file, write the meta
         # and then write the data?
         # do we touch a temporary file, write the meta