--- a/CHANGES.txt	Fri Jun 10 21:28:40 2016 -0400
+++ b/CHANGES.txt	Fri Jun 10 23:33:11 2016 -0400
@@ -69,6 +69,13 @@
 - issue2550907 Fix errors when creating documentation. Work done by
   Peter Funk (pefu). (Applied by John Rouillard with small change
   omitting obsolete security.txt.)
+- issue2550826 Capture all exceptions from auditors/reactors and
+  raise a DetectorError instead. This allows failures like IOErrors
+  from the detectors (e.g. unable to access files) to be handled.
+  Previously an IOError just resulted in no output (premature end of
+  headers under apache). Problem diagnosed and initial patch created by
+  Tom Ekberg (tekberg). Further testing and patch change done by
+  John Rouillard.
 
 2016-01-11: 1.5.1
 

--- a/roundup/cgi/client.py	Fri Jun 10 21:28:40 2016 -0400
+++ b/roundup/cgi/client.py	Fri Jun 10 23:33:11 2016 -0400
@@ -19,7 +19,7 @@
 from roundup.exceptions import LoginError, Reject, RejectRaw, Unauthorised
 from roundup.cgi.exceptions import (
     FormError, NotFound, NotModified, Redirect, SendFile, SendStaticFile,
-    SeriousError)
+    DetectorError, SeriousError)
 from roundup.cgi.form_parser import FormParser
 from roundup.mailer import Mailer, MessageSendError, encode_quopri
 from roundup.cgi import accept_language
@@ -572,6 +572,15 @@
             # OpenSSL.SSL.SysCallError is similar to IOError above
             # may happen during write_html and serve_file, too.
             pass
+        except DetectorError as e:
+            if not self.instance.config.WEB_DEBUG:
+                # run when we are not in debug mode, so errors
+                # go to admin too.
+                self.send_error_to_admin(e.subject, e.html, e.txt)
+                self.write_html(e.html)
+            else:
+                # in debug mode, only write error to screen.
+                self.write_html(e.html)
         except:
             # Something has gone badly wrong.  Therefore, we should
             # make sure that the response code indicates failure.

--- a/roundup/cgi/exceptions.py	Fri Jun 10 21:28:40 2016 -0400
+++ b/roundup/cgi/exceptions.py	Fri Jun 10 23:33:11 2016 -0400
@@ -18,6 +18,14 @@
 class NotModified(HTTPException):
     pass
 
+class DetectorError(Exception):
+    """Raised when a detector throws an exception.
+Contains details of the exception."""
+    def __init__(self, subject, html, txt):
+        self.subject = subject
+        self.html = html
+        self.txt = txt
+
 class FormError(ValueError):
     """An 'expected' exception occurred during form parsing.
 

--- a/roundup/hyperdb.py	Fri Jun 10 21:28:40 2016 -0400
+++ b/roundup/hyperdb.py	Fri Jun 10 23:33:11 2016 -0400
@@ -21,12 +21,14 @@
 __docformat__ = 'restructuredtext'
 
 # standard python modules
-import os, re, shutil, weakref
+import os, re, shutil, sys, weakref
+import traceback
 
 # roundup modules
 import date, password
 from support import ensureParentsExist, PrioList
 from roundup.i18n import _
+from roundup.cgi.exceptions import DetectorError
 
 #
 # Types
@@ -1290,7 +1292,16 @@
     def fireAuditors(self, event, nodeid, newvalues):
         """Fire all registered auditors"""
         for prio, name, audit in self.auditors[event]:
-            audit(self.db, self, nodeid, newvalues)
+            try:
+                audit(self.db, self, nodeid, newvalues)
+            except Exception as e:
+                tb = traceback.format_exc()
+                html = ("<h1>Traceback</h1>" + str(tb).replace('\n', '<br>').
+                        replace(' ', '&nbsp;'))
+                txt = 'Caught exception %s: %s\n%s' % (str(type(e)), e, tb)
+                exc_info = sys.exc_info()
+                subject = "Error: %s" % exc_info[1]
+                raise DetectorError(subject, html, txt)
 
     def react(self, event, detector, priority = 100):
         """Register a reactor detector"""
@@ -1299,7 +1310,16 @@
     def fireReactors(self, event, nodeid, oldvalues):
         """Fire all registered reactors"""
         for prio, name, react in self.reactors[event]:
-            react(self.db, self, nodeid, oldvalues)
+            try:
+                react(self.db, self, nodeid, oldvalues)
+            except Exception as e:
+                tb = traceback.format_exc()
+                html = ("<h1>Traceback</h1>" + str(tb).replace('\n', '<br>').
+                        replace(' ', '&nbsp;'))
+                txt = 'Caught exception %s: %s\n%s' % (str(type(e)), e, tb)
+                exc_info = sys.exc_info()
+                subject = "Error: %s" % exc_info[1]
+                raise DetectorError(subject, html, txt)
 
     #
     # import / export support