The httplib.HTTPConnection API changed from python2.6 to python2.7. These changes are reflected in the handleErrors property of zope.testbrowser.browser.Browser - it is no longer possible to pass a boolean into the request headers. A fix is available on the trunk of zope.testbrowser [1]. In this implementation, a boolean is provided to the consumers of the testbrowser API and a string is used in the request headers. This implementation is sub-optimal in my opinion. In the branch 'janjaapdriessen-handle-errors' [2] you will find a cleaner implementation, where the switch to handle_errors is controlled by the presence of a "zope-do-not-handle-errors" header. The value of the header is no longer interpreted. This change is backwards incompatible. Code relying on the 'x-zope-handle-errors' header will break. I have tested this implementation against the ZTK trunk on python2.7 and have found no breakage of this kind. Please let me know if either of these solutions is OK with you. If so, grant me pypi rights (my handle is 'janjaapdriessen') so I can release zope.testbrowser and get a step closer to making the ZTK run on python2.7. Thanks, -- Jan-Jaap Driessen 1) svn.zope.org/repos/main/zope.testbrowser/trunk 2) svn.zope.org/repos/main/zope.testbrowser/branches/janjaapdriessen-handle-errors