Change default loader for yaml.add_constructor (#287)

* Change default loader for yaml.add_constructor

If the Loader parameter is not given, add constructor to
all three loaders

lib/yaml/__init__.py

diff --git a/lib/yaml/__init__.py b/lib/yaml/__init__.py
index 5d56d65..a9db6a3 100644
--- a/lib/yaml/__init__.py
+++ b/lib/yaml/__init__.py
@@ -329,22 +329,32 @@
     Loader.add_path_resolver(tag, path, kind)
     Dumper.add_path_resolver(tag, path, kind)
 
-def add_constructor(tag, constructor, Loader=Loader):
+def add_constructor(tag, constructor, Loader=None):
     """
     Add a constructor for the given tag.
     Constructor is a function that accepts a Loader instance
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_constructor(tag, constructor)
+    if Loader == None:
+        loader.Loader.add_constructor(tag, constructor)
+        loader.FullLoader.add_constructor(tag, constructor)
+        loader.UnsafeLoader.add_constructor(tag, constructor)
+    else:
+        Loader.add_constructor(tag, constructor)
 
-def add_multi_constructor(tag_prefix, multi_constructor, Loader=Loader):
+def add_multi_constructor(tag_prefix, multi_constructor, Loader=None):
     """
     Add a multi-constructor for the given tag prefix.
     Multi-constructor is called for a node if its tag starts with tag_prefix.
     Multi-constructor accepts a Loader instance, a tag suffix,
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_multi_constructor(tag_prefix, multi_constructor)
+    if Loader == None:
+        loader.Loader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.FullLoader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.UnsafeLoader.add_multi_constructor(tag_prefix, multi_constructor)
+    else:
+        Loader.add_multi_constructor(tag_prefix, multi_constructor)
 
 def add_representer(data_type, representer, Dumper=Dumper):
     """

lib3/yaml/__init__.py

diff --git a/lib3/yaml/__init__.py b/lib3/yaml/__init__.py
index 3f499d3..ac0b702 100644
--- a/lib3/yaml/__init__.py
+++ b/lib3/yaml/__init__.py
@@ -326,22 +326,32 @@
     Loader.add_path_resolver(tag, path, kind)
     Dumper.add_path_resolver(tag, path, kind)
 
-def add_constructor(tag, constructor, Loader=Loader):
+def add_constructor(tag, constructor, Loader=None):
     """
     Add a constructor for the given tag.
     Constructor is a function that accepts a Loader instance
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_constructor(tag, constructor)
+    if Loader == None:
+        loader.Loader.add_constructor(tag, constructor)
+        loader.FullLoader.add_constructor(tag, constructor)
+        loader.UnsafeLoader.add_constructor(tag, constructor)
+    else:
+        Loader.add_constructor(tag, constructor)
 
-def add_multi_constructor(tag_prefix, multi_constructor, Loader=Loader):
+def add_multi_constructor(tag_prefix, multi_constructor, Loader=None):
     """
     Add a multi-constructor for the given tag prefix.
     Multi-constructor is called for a node if its tag starts with tag_prefix.
     Multi-constructor accepts a Loader instance, a tag suffix,
     and a node object and produces the corresponding Python object.
     """
-    Loader.add_multi_constructor(tag_prefix, multi_constructor)
+    if Loader == None:
+        loader.Loader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.FullLoader.add_multi_constructor(tag_prefix, multi_constructor)
+        loader.UnsafeLoader.add_multi_constructor(tag_prefix, multi_constructor)
+    else:
+        Loader.add_multi_constructor(tag_prefix, multi_constructor)
 
 def add_representer(data_type, representer, Dumper=Dumper):
     """