test fixups

integration/util.py

@@ -199,10 +199,24 @@ def _create_node(reactor, request, temp_dir, introducer_furl, flog_gatherer, nam
     return d
 
 
-def await_file_contents(path, contents, timeout=15):
+def await_file_contents(path, contents, timeout=15, error_if=None):
+    """
+    wait up to `timeout` seconds for the file at `path` to have the
+    exact content `contents.
+
+    :param error_if: if specified, a list of additional paths; if any
+        of these paths appear an Exception is raised.
+    """
     start_time = time.time()
     while time.time() - start_time < timeout:
         print("  waiting for '{}'".format(path))
+        if error_if and any([exists(p) for p in error_if]):
+            raise Exception(
+                "While waiting for '{}', unwanted files appeared: {}".format(
+                    path,
+                    ', '.join([p for p in error_if if exists(p)]),
+                )
+            )
         if exists(path):
             try:
                 with open(path, 'r') as f: