Ignore OSError in devserver

psutil does not work properly in builder. The load info of devserver has no
use in devserver anyway. Ignore such error when importing psutil.

BUG=chromium:498053
TEST=local run devserver
curl http://localhost:8082/check_health

Change-Id: I29116b2d44c72fea276782b45d949b1005c034d9
Reviewed-on: https://chromium-review.googlesource.com/276247
Reviewed-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
Trybot-Ready: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
diff --git a/devserver.py b/devserver.py
index b2c57e7..b4bb063 100755
--- a/devserver.py
+++ b/devserver.py
@@ -82,6 +82,14 @@
   _Log('Python module psutil is not installed, devserver load data will not be '
        'collected')
   psutil = None
+except OSError as e:
+  # Ignore error like following. psutil may not work properly in builder. Ignore
+  # the error as load information of devserver is not used in builder.
+  # OSError: [Errno 2] No such file or directory: '/dev/pts/0'
+  _Log('psutil is failed to be imported, error: %s. devserver load data will '
+       'not be collected.', e)
+  psutil = None
+
 
 CACHED_ENTRIES = 12