[perf-web] Fix error with timezone setting

[Owen Taylor <otaylor src gnome org>]

commit a6925526750b23824c55fd782984dbd22f35bdf5
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Fri Jul 25 12:05:34 2014 +0200

    Fix error with timezone setting
    
    datetime.replace() returns a new datetime, it doesn't mutate.

 metrics/views.py |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)
---
diff --git a/metrics/views.py b/metrics/views.py
index 136dbbf..5140714 100644
--- a/metrics/views.py
+++ b/metrics/views.py
@@ -330,8 +330,7 @@ def process_report(data, machine_name):
 
     pull_time_str = child_string(data, 'pullTime')
     try:
-        pull_time = datetime.strptime(pull_time_str, '%Y-%m-%d %H:%M:%S')
-        pull_time.replace(tzinfo=timezone.utc)
+        pull_time = datetime.strptime(pull_time_str, '%Y-%m-%d %H:%M:%S').replace(tzinfo=timezone.utc)
     except ValueError:
         raise ValidationError("Can't parse property 'pullTime'")