Be sure the temporary directory exists

src/allmydata/test/web/test_web.py

@@ -6,6 +6,9 @@ import treq
 
 from bs4 import BeautifulSoup
 
+from twisted.python.filepath import (
+    FilePath,
+)
 from twisted.application import service
 from twisted.internet import defer
 from twisted.internet.defer import inlineCallbacks, returnValue
@@ -316,10 +319,12 @@ class WebMixin(TimezoneMixin):
         self.staticdir = self.mktemp()
         self.clock = Clock()
         self.fakeTime = 86460 # 1d 0h 1m 0s
+        tempdir = FilePath(self.mktemp())
+        tempdir.makedirs()
         self.ws = webish.WebishServer(
             self.s,
             "0",
-            tempdir=self.mktemp(),
+            tempdir=tempdir.path,
             staticdir=self.staticdir,
             clock=self.clock,
             now_fn=lambda:self.fakeTime,