py3: Bump `sourcemap` dependency to get py3 bugfix.

The one difference between `sourcemap` 0.2.0 and 0.2.1 is this fix:
  https://github.com/mattrobenolt/python-sourcemap/pull/9
This addresses an issue that caused the Zulip server running on
Python 3 to raise exceptions when attempting to process a JS error.

requirements/common.txt

@@ -125,7 +125,7 @@ smmap==0.9.0
 sockjs-tornado==1.0.3
 
 # Needed to parse source maps for error reporting
-sourcemap==0.2.0
+sourcemap==0.2.1
 
 # Tornado used for server->client push system
 tornado==4.5.1

requirements/py2_common_lock.txt

@@ -98,7 +98,7 @@ smmap==0.9.0
 social-auth-app-django==1.2.0
 social-auth-core==1.4.0
 sockjs-tornado==1.0.3
-sourcemap==0.2.0
+sourcemap==0.2.1
 sqlalchemy==1.1.10
 statsd==2.1.2             # via django-statsd-mozilla
 tornado==4.5.1

requirements/py3_common_lock.txt

@@ -89,7 +89,7 @@ smmap==0.9.0
 social-auth-app-django==1.2.0
 social-auth-core==1.4.0
 sockjs-tornado==1.0.3
-sourcemap==0.2.0
+sourcemap==0.2.1
 sqlalchemy==1.1.10
 statsd==2.1.2             # via django-statsd-mozilla
 tornado==4.5.1