PyPy compatible louie.robustapply.function implementation

Based on PR #3 - thanks @svpcom!

.travis.yml

@@ -8,6 +8,7 @@ python:
   - "3.5"
   - "3.5-dev" # 3.5 development branch
   - "nightly" # currently points to 3.6-dev
+  - "pypy"
 # command to install dependencies
 install: "pip install -e ."
 # command to run tests

doc/contributors.rst

@@ -11,3 +11,5 @@ The following people have contributed code to PyDispatcher and Louie:
 - `Matthew R. Scott <https://github.com/gldnspud>`__
 
 - `Brad Arndt <https://github.com/digdugg>`__
+
+- `Vasily Evseenko <https://github.com/svpcom>`__

louie/robustapply.py

@@ -5,6 +5,15 @@
 those which are acceptable.
 """
 
+import sys
+if sys.hexversion >= 0x3000000:
+    IM_FUNC = '__func__'
+    FUNC_CODE = '__code__'
+else:
+    IM_FUNC = 'im_func'
+    FUNC_CODE = 'func_code'
+
+
 def function(receiver):
     """Get function-like callable object for given receiver.
 
@@ -13,28 +22,19 @@ def function(receiver):
     If fromMethod is true, then the callable already has its first
     argument bound.
     """
-    if hasattr(receiver, '__call__'):
-        # receiver is a class instance; assume it is callable.
-        # Reassign receiver to the actual method that will be called.
-        c = receiver.__call__
-        if hasattr(c, 'im_func') or hasattr(c, 'im_code'):
-            receiver = c 
-        if hasattr(c, '__func__') or hasattr(c, '__code__'):
-            receiver = c
-    if hasattr(receiver, 'im_func'):
-        # receiver is an instance-method.
-        return receiver, receiver.im_func.func_code, 1
-    if hasattr(receiver, '__func__'):
-        #receiver is an instance method in python3
-        return receiver, receiver.__func__.__code__, 1
-    if hasattr(receiver, '__code__'):
-        #receiver is a function and has code, name changed in python3?
-        return receiver, receiver.__code__, 0 
-
-    elif not hasattr(receiver, 'func_code'):
+    if hasattr(receiver, IM_FUNC):
+        # Instance method.
+        im_func = getattr(receiver, IM_FUNC)
+        func_code = getattr(im_func, FUNC_CODE)
+        return receiver, func_code, True
+    elif hasattr(receiver, FUNC_CODE):
+        func_code = getattr(receiver, FUNC_CODE)
+        return receiver, func_code, False
+    elif hasattr(receiver, '__call__'):
+        return function(receiver.__call__)
+    else:
         raise ValueError(
             'unknown reciever type {} {}'.format(receiver, type(receiver)))
-    return receiver, receiver.func_code, 0
 
 
 def robust_apply(receiver, signature, *arguments, **named):