Prevent traceback.

https://github.com/ansible/ansible/issues/13743#issuecomment-171520585

In some circumstance, the file fails to open.  When that occurs, we
can't try to close it in the finally clause.  Using a context manager is
the cleanest way to change the code to account for that case.

lib/ansible/galaxy/role.py

@@ -130,13 +130,11 @@ class GalaxyRole(object):
             install_date=datetime.datetime.utcnow().strftime("%c"),
         )
         info_path = os.path.join(self.path, self.META_INSTALL)
-        try:
-            f = open(info_path, 'w+')
-            self._install_info = yaml.safe_dump(info, f)
-        except:
-            return False
-        finally:
-            f.close()
+        with open(info_path, 'w+') as f:
+            try:
+                self._install_info = yaml.safe_dump(info, f)
+            except:
+                return False
 
         return True