[Findit] Make Findit more robust.

tools/findit/findit_for_clusterfuzz.py

 # Copyright (c) 2014 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 sys
+
 import chromium_deps
 from common import utils
 import crash_utils
 import findit_for_crash as findit
 import stacktrace
 
 
 def SplitStacktrace(stacktrace_string):
   """Preprocesses stacktrace string into two parts, release and debug.
 
@@ skipping 86 matching lines @@
   chrome_regression = crash_utils.SplitRange(chrome_regression)
   if chrome_regression:
     chrome_regression_start = chrome_regression[0]
     chrome_regression_end = chrome_regression[1]
 
     # Do not parse regression information for crashes introduced before the
     # first archived build.
     if chrome_regression_start != '0':
       component_to_regression_dict = chromium_deps.GetChromiumComponentRange(
           chrome_regression_start, chrome_regression_end)
+      if not component_to_regression_dict:
+        print ('Failed to get component regression ranges for chromium '
+               'regression range %s:%s'
+               % (chrome_regression_start, chrome_regression_end))
+        sys.exit(1)
 
   # Parse crash revision.
   if chrome_crash_revision:
     component_to_crash_revision_dict = chromium_deps.GetChromiumComponents(
         chrome_crash_revision)
+    if not component_to_crash_revision_dict:
+      print ('Failed to get component dependencies for chromium revision "%s".'
+             % chrome_crash_revision)
+      sys.exit(1)
 
   # Check if component regression information is available.
   component_regression = crash_utils.SplitRange(component_regression)
   if component_regression:
     component_regression_start = component_regression[0]
     component_regression_end = component_regression[1]
 
     # If this component already has an entry in parsed DEPS file, overwrite
     # regression range and url.
     if crashing_component_path in component_to_regression_dict:
@@ skipping 74 matching lines @@
   # build stacktrace in higher priority than debug build stacktace. This stack
   # is the callstack to find blame information for.
   if parsed_release_build_stacktrace.stack_list:
     main_stack = parsed_release_build_stacktrace.GetCrashStack()
   elif parsed_debug_build_stacktrace.stack_list:
     main_stack = parsed_debug_build_stacktrace.GetCrashStack()
   else:
     if 'mac_' in build_type:
       return ('No line information available in stacktrace.', [])
 
-    return ('Stacktrace is malformed.', [])
+    return ('Findit failed to find any stack trace. Is it in a new format?', [])
 
   # Run the algorithm on the parsed stacktrace, and return the result.
   stacktrace_list = [parsed_release_build_stacktrace,
                      parsed_debug_build_stacktrace]
   return findit.FindItForCrash(
       stacktrace_list, main_stack, component_to_regression_dict,
       component_to_crash_revision_dict)