fix: prefer attr over key lookup when getting model values

applies to both forms and grids.

the base model class can still handle `obj[key]` but now it is limited
to the column fields only, no association proxies.

so, better to just try `getattr(obj, key)` first and only fall back to
the other if it fails.

unless the obj is clearly a dict in which case try `obj[key]` only

tailbone/forms/core.py

@@ -1359,12 +1359,15 @@ class Form(object):
 
     def obtain_value(self, record, field_name):
         if record:
-            try:
+
+            if isinstance(record, dict):
+                return record[field_name]
+
+            try:
+                return getattr(record, field_name)
+            except AttributeError:
+                pass
             return record[field_name]
-            except KeyError:
-                return None
-            except TypeError:
-                return getattr(record, field_name, None)
 
         # TODO: is this always safe to do?
         elif self.defaults and field_name in self.defaults:

tailbone/grids/core.py

@@ -586,12 +586,14 @@ class Grid(WuttaGrid):
         if isinstance(obj, sa.engine.Row):
             return obj._mapping[column_name]
 
-        try:
+        if isinstance(obj, dict):
             return obj[column_name]
-        except KeyError:
+
+        try:
+            return getattr(obj, column_name)
+        except AttributeError:
             pass
-        except TypeError:
-            return getattr(obj, column_name, None)
+        return obj[column_name]
 
     def render_currency(self, obj, column_name):
         value = self.obtain_value(obj, column_name)