Convert arguments to ''.join() to strings in tools/utils.py

tools/utils.py

Index: tools/utils.py
diff --git a/tools/utils.py b/tools/utils.py
index da2cd28892b25e9d8eb5eb306e86d623bd5a6a76..d42abb15ca4de1791313fd73938d5578e719afa6 100644
--- a/tools/utils.py
+++ b/tools/utils.py
@@ -696,7 +696,7 @@ class ChangedWorkingDirectory(object):
 class UnexpectedCrash(object):
   def __init__(self, test, pid, binary):
     self.test = test
-    self.pid = pid 
+    self.pid = pid
     self.binary = binary
 
   def __str__(self):
@@ -849,7 +849,8 @@ class BaseCoreDumpArchiver(object):
         missing.append(crash)
     self._upload(files)
     if missing:
-      raise Exception('Missing crash dumps for: %s' % ', '.join(missing))
+      raise Exception('Missing crash dumps for: %s' % ', '.join(
+          [str(c) for c in missing]))
 
   def _upload(self, files):
     bot_utils = GetBotUtils()