Avoid running some test layers in a subprocess

The default of allowTearDown=False is just caution; it seems to be safe
here.

Author: mgedmin

src/zope/file/testing.py

@@ -34,8 +34,6 @@
 from zope.publisher.browser import BrowserView
 from zope.publisher.interfaces.browser import IBrowserPublisher
 
-from zope.security.proxy import removeSecurityProxy
-
 from zope.traversing.browser.absoluteurl import absoluteURL
 
 import zope.app.wsgi.testlayer
@@ -49,7 +47,7 @@ class BrowserLayer(zope.testbrowser.wsgi.TestBrowserLayer,
     pass
 
 
-ZopeFileLayer = BrowserLayer(zope.file)
+ZopeFileLayer = BrowserLayer(zope.file, allowTearDown=True)
 
 
 class _FakeResponse(FakeResponse):