policies/expression: migrate to raw python instead of jinja2 (#49)

* policies/expression: migrate to raw python instead of jinja2

* lib/expression: create base evaluator, custom subclass for policies

* core: rewrite propertymappings to use python

* providers/saml: update to new PropertyMappings

* sources/ldap: update to new PropertyMappings

* docs: update docs for new propertymappings

* root: remove jinja2

* root: re-add jinja to lock file as its implicitly required

passbook/providers/saml/forms.py

@@ -4,6 +4,7 @@ from django import forms
 from django.contrib.admin.widgets import FilteredSelectMultiple
 from django.utils.translation import gettext as _
 
+from passbook.core.expression import PropertyMappingEvaluator
 from passbook.providers.saml.models import (
     SAMLPropertyMapping,
     SAMLProvider,
@@ -52,6 +53,13 @@ class SAMLPropertyMappingForm(forms.ModelForm):
 
     template_name = "saml/idp/property_mapping_form.html"
 
+    def clean_expression(self):
+        """Test Syntax"""
+        expression = self.cleaned_data.get("expression")
+        evaluator = PropertyMappingEvaluator()
+        evaluator.validate(expression)
+        return expression
+
     class Meta:
 
         model = SAMLPropertyMapping