Comment 5 for bug 1781381

It seems more appropriate to update the request object instead. With your patch, you'll ignore added headers(including the crumb).
To prevent this, just change the request instanciation for the delete_build call (wipeout_job_workspace has the same call so it fixes that as well):

diff --git a/jenkins/__init__.py b/jenkins/__init__.py
index 620ce14..0691f2a 100755
--- a/jenkins/__init__.py
+++ b/jenkins/__init__.py
@@ -1469,7 +1469,7 @@ class Jenkins(object):
         """
         folder_url, short_name = self._get_job_folder(name)
         self.jenkins_open(requests.Request('POST',
- self._build_url(DELETE_BUILD, locals()), b''))
+ self._build_url(DELETE_BUILD, locals())))

     def wipeout_job_workspace(self, name):
         """Wipe out workspace for given Jenkins job.
@@ -1479,7 +1479,7 @@ class Jenkins(object):
         folder_url, short_name = self._get_job_folder(name)
         self.jenkins_open(requests.Request('POST',
                           self._build_url(WIPEOUT_JOB_WORKSPACE,
- locals()), b''))
+ locals())))

     def get_running_builds(self):
         '''Return list of running builds.