Fix flaky DHCP tests in CI (#129327)

tests/components/dhcp/conftest.py

@@ -0,0 +1,21 @@
+"""Tests for the dhcp integration."""
+
+import os
+import pathlib
+
+
+def pytest_sessionstart(session):
+    """Try to avoid flaky FileExistsError in CI.
+
+    Called after the Session object has been created and
+    before performing collection and entering the run test loop.
+
+    This is needed due to a race condition in scapy v2.6.0
+    See https://github.com/secdev/scapy/pull/4558
+
+    Can be removed when scapy 2.6.1 is released.
+    """
+    for sub_dir in (".cache", ".config"):
+        path = pathlib.Path(os.path.join(os.path.expanduser("~"), sub_dir))
+        if not path.exists():
+            path.mkdir(mode=0o700, exist_ok=True)