Update for autogen.py to include the content of constraints.py
diff --git a/docs/autogen.py b/docs/autogen.py
index f8fcb380f41..808307589e0 100644
--- a/docs/autogen.py
+++ b/docs/autogen.py
@@ -80,6 +80,7 @@
 from keras import losses
 from keras import metrics
 from keras import backend
+from keras import constraints
 from keras import activations
 from keras import preprocessing
 
@@ -327,6 +328,10 @@
         'page': 'backend.md',
         'all_module_functions': [backend],
     },
+    {
+        'page': 'constraints.md',
+        'all_module_classes': [constraints],
+    },
     {
         'page': 'utils.md',
         'functions': [utils.to_categorical,
diff --git a/docs/templates/constraints.md b/docs/templates/constraints.md
index e997fd2774f..ca39abe0c23 100644
--- a/docs/templates/constraints.md
+++ b/docs/templates/constraints.md
@@ -17,7 +17,9 @@ model.add(Dense(64, kernel_constraint=max_norm(2.)))
 
 ## Available constraints
 
-- __max_norm(max_value=2, axis=0)__: maximum-norm constraint
-- __non_neg()__: non-negativity constraint
-- __unit_norm(axis=0)__: unit-norm constraint
-- __min_max_norm(min_value=0.0, max_value=1.0, rate=1.0, axis=0)__:  minimum/maximum-norm constraint
+---
+
+{{autogenerated}}
+
+---
+

### Summary
Information from the docstrings of the file constraints.py was not grabbed by autogen.py because the autogenerated code block was absent in templates/constraints.md and the corresponsing part of the PAGES list in autogen.py was not there too. I did not find a commit where it would work before, but i could have missed it.

### Related Issues
Resolves the issue #11382
### PR Overview

- [n] This PR requires new unit tests [y/n] (make sure tests are included)
- [y] This PR requires to update the documentation [y/n] (make sure the docs are up-to-date)
- [y] This PR is backwards compatible [y/n]
- [n] This PR changes the current API [y/n] (all API changes need to be approved by fchollet)