Check for errors of cryptohome-path.

tools/telemetry/telemetry/core/backends/chrome/cros_interface.py

Index: tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
diff --git a/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py b/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
index bad60225fd7651b77312ddb8cc86495419b8b7df..b5add7d4e9ffef3f6f57de299a661d5c8c2fa5a2 100644
--- a/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
+++ b/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
@@ -196,7 +196,7 @@ class CrOSInterface(object):
       if "Connection timed out" in stderr:
         raise OSError('Machine wasn\'t responding to ssh: %s' %
                       stderr)
-      raise OSError('Unepected error: %s' % stderr)
+      raise OSError('Unexpected error: %s' % stderr)
     exists = stdout == '1\n'
     logging.debug("FileExistsOnDevice(<text>, %s)->%s" % (file_name, exists))
     return exists
@@ -401,8 +401,11 @@ class CrOSInterface(object):
 
   def CryptohomePath(self, user):
     """Returns the cryptohome mount point for |user|."""
-    return self.RunCmdOnDevice(
-        ['cryptohome-path', 'user', "'%s'" % user])[0].strip()
+    stdout, stderr = self.RunCmdOnDevice(
+        ['cryptohome-path', 'user', "'%s'" % user])
+    if stderr != '':
+      raise OSError('cryptohome-path failed: %s' % stderr)
+    return stdout.rstrip()
 
   def IsCryptohomeMounted(self, username, is_guest):
     """Returns True iff |user|'s cryptohome is mounted."""