test: run the printed override line without inherited variables

test_override_command_carries_prefix_ref_and_base_url ran the printed
--force line with the fixture env, which already exports
PYMOLSCRIPTS_REF and PYMOLSCRIPTS_BASE_URL, so a line that set neither
for the installer still passed: moving the assignments onto curl's side
of the pipe (install.sh) or commenting out the $env: assignments
(install.ps1) left all tests green.

The line now runs with both variables pointing where the local server
publishes nothing, so it succeeds only when it sets them itself; both
mutations fail with a local 404. Unsetting them instead would let a
broken line fall back to the real base URL.

Author: FridrichMethod

tests/test_local_edits.py

@@ -66,6 +66,17 @@ def override_line(self, result):
         self.assertTrue(lines, self.describe(result))
         return lines[-1].strip()
 
+    def override_env(self):
+        """self.env with PYMOLSCRIPTS_REF and PYMOLSCRIPTS_BASE_URL pointing
+        where the local server publishes nothing, so that a printed override
+        line works only when it sets both itself. Unsetting them instead
+        would let a broken line fall back to the real base URL."""
+        return dict(
+            self.env,
+            PYMOLSCRIPTS_REF="wrongref",
+            PYMOLSCRIPTS_BASE_URL=f"{self.server.base_url}/wrong",
+        )
+
     # --- recording ----------------------------------------------------------
 
     def test_install_records_what_it_wrote(self):
@@ -375,7 +386,7 @@ def run_override(self, line):
             self.skipTest("curl not found")
         self.server.publish_script("testref", self.script_name)
         result = subprocess.run(
-            ["/bin/sh", "-c", line], env=self.env, stdin=subprocess.DEVNULL,
+            ["/bin/sh", "-c", line], env=self.override_env(), stdin=subprocess.DEVNULL,
             capture_output=True, timeout=180,
         )
         self.assertEqual(result.returncode, 0, self.describe(result))
@@ -437,7 +448,7 @@ def run_override(self, line):
         self.server.publish_script("testref", self.script_name)
         result = subprocess.run(
             [self.exe, "-NoLogo", "-NoProfile", "-NonInteractive", "-Command", line],
-            env=self.env, stdin=subprocess.DEVNULL, capture_output=True, timeout=180,
+            env=self.override_env(), stdin=subprocess.DEVNULL, capture_output=True, timeout=180,
         )
         self.assertEqual(result.returncode, 0, self.describe(result))