Do not guess it is a webdav request if the http method is purge

doc/CHANGES.rst

@@ -16,6 +16,8 @@ http://docs.zope.org/zope2/releases/.
 
 - ZPublisher: Do not assume that you can iterate over a publishable object
 
+- ZPublisher: Do not guess it is a webdav request if the http method is purge
+
 2.13.15 (2012-06-22)
 --------------------
 

src/ZPublisher/BaseRequest.py

@@ -379,7 +379,7 @@ class BaseRequest:
         # How did this request come in? (HTTP GET, PUT, POST, etc.)
         method = request_get('REQUEST_METHOD', 'GET').upper()
 
-        if method=='GET' or method=='POST' and not isinstance(response,
+        if method in ["GET", "POST", "PURGE"] and not isinstance(response,
                                                               xmlrpc.Response):
             # Probably a browser
             no_acquire_flag=0