migrate SCREENSHOT_DIR to new env var system

reflex/config.py

@@ -500,6 +500,9 @@ class EnvironmentVariables:
     # Arguments to pass to the app harness driver.
     APP_HARNESS_DRIVER_ARGS: EnvVar[str] = env_var("")
 
+    # Where to save screenshots when tests fail.
+    SCREENSHOT_DIR: EnvVar[Optional[Path]] = env_var(None)
+
 
 environment = EnvironmentVariables()
 

tests/integration/conftest.py

@@ -43,7 +43,7 @@ def pytest_exception_interact(node, call, report):
         call: The pytest call describing when/where the test was invoked.
         report: The pytest log report object.
     """
-    screenshot_dir = os.environ.get("SCREENSHOT_DIR")
+    screenshot_dir = environment.SCREENSHOT_DIR.get
     if DISPLAY is None or screenshot_dir is None:
         return