Use auto resource management for license file (#330)

Author: hduelme

usr/lib/webapp-manager/webapp-manager.py

@@ -238,12 +238,8 @@ def open_about(self, widget):
         dlg.set_program_name(_("Web Apps"))
         dlg.set_comments(_("Run websites as if they were apps"))
         try:
-            h = open('/usr/share/common-licenses/GPL', encoding="utf-8")
-            s = h.readlines()
-            gpl = ""
-            for line in s:
-                gpl += line
-            h.close()
+            with open('/usr/share/common-licenses/GPL', encoding="utf-8") as h:
+                gpl = h.read()
             dlg.set_license(gpl)
         except Exception as e:
             print(e)