build fix

snakehouse/satella.py

@@ -4,6 +4,7 @@ cut off the dependency and allow earlier Pythons to use
 snakehouse.
 """
 import typing as tp
+import os
 
 
 def _has_separator(path: str) -> bool:
@@ -81,4 +82,4 @@ def split(path: str) -> tp.List[str]:
         data = list(os.path.split(data[0])) + data[1:]
     return dataator(data[0]):
         data = list(os.path.split(data[0])) + data[1:]
-    return data
\ No newline at end of file
+    return data