[Telemetry] Include debugging info when foreground tab is missing

telemetry/telemetry/internal/browser/browser.py

 # Copyright 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import logging
 import sys
 
 from py_utils import cloud_storage  # pylint: disable=import-error
 
 from telemetry.core import exceptions
@@ skipping 85 matching lines @@
   @property
   def foreground_tab(self):
     for i in xrange(len(self._tabs)):
       # The foreground tab is the first (only) one that isn't hidden.
       # This only works through luck on Android, due to crbug.com/322544
       # which means that tabs that have never been in the foreground return
       # document.hidden as false; however in current code the Android foreground
       # tab is always tab 0, which will be the first one that isn't hidden
       if self._tabs[i].EvaluateJavaScript('!document.hidden'):
         return self._tabs[i]
-    raise Exception("No foreground tab found")
+    raise exceptions.TabMissingError("No foreground tab found")
 
   @property
   @decorators.Cache
   def extensions(self):
     if not self.supports_extensions:
       raise browser_backend.ExtensionsNotSupportedException(
           'Extensions not supported')
     return extension_dict.ExtensionDict(self._browser_backend.extension_backend)
 
   def _LogBrowserInfo(self):
@@ skipping 277 matching lines @@
     except Exception: # pylint: disable=broad-except
       logging.exception('Failed to get browser standard output:')
     logging.info('*********** END OF BROWSER STANDARD OUTPUT ************')
 
     logging.info('********************* BROWSER LOG *********************')
     try:
       logging.info(self.GetLogFileContents())
     except Exception: # pylint: disable=broad-except
       logging.exception('Failed to get browser log:')
     logging.info('***************** END OF BROWSER LOG ******************')