fix: detect uv environments

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

nox/virtualenv.py

@@ -350,21 +350,21 @@ def _clean_location(self) -> bool:
 
     def _check_reused_environment_type(self) -> bool:
         """Check if reused environment type is the same."""
-        path = os.path.join(self.location, "pyvenv.cfg")
-        if not os.path.isfile(path):
+        try:
+            with open(os.path.join(self.location, "pyvenv.cfg")) as fp:
+                parts = (x.partition("=") for x in fp if "=" in x)
+                config = {k.strip(): v.strip() for k, _, v in parts}
+            if "gourgeist" in config:
+                old_env = "uv"
+            elif "virtualenv" in config:
+                old_env = "virtualenv"
+            else:
+                old_env = "venv"
+        except FileNotFoundError:
             # virtualenv < 20.0 does not create pyvenv.cfg
             old_env = "virtualenv"  # pragma: win32 no cover
-        else:
-            pattern = re.compile("virtualenv[ \t]*=")
-            with open(path) as fp:
-                old_env = (
-                    "virtualenv" if any(pattern.match(line) for line in fp) else "venv"
-                )
-        # We can't distinguish a uv env from a venv env, so just treat them
-        # the same.
-        return old_env == self.venv_backend or (
-            {old_env, self.venv_backend} == {"uv", "venv"}
-        )
+
+        return old_env == self.venv_backend
 
     def _check_reused_environment_interpreter(self) -> bool:
         """Check if reused environment interpreter is the same."""