admin: don't present signing option if M2Crypto is not available

wcs/admin/forms.ptl

@@ -22,6 +22,11 @@ except ImportError:
     except ImportError:
         ET = None
 
+try:
+    import M2Crypto
+except ImportError:
+    M2Crypto = None
+
 import tarfile
 import time
 from cStringIO import StringIO
@@ -537,7 +542,8 @@ class FormDefPage(Directory):
         form = Form(enctype='multipart/form-data')
         form.add(CheckboxWidget, 'confirmation', title=_('Include confirmation page'),
                 value=self.formdef.confirmation)
-        form.add(SingleSelectWidget, 'signing', title=_('Signature'),
+        if M2Crypto:
+            form.add(SingleSelectWidget, 'signing', title=_('Signature'),
                         value=self.formdef.signing,
                         options = [
                                 (None, _('None')),