bind: fix py3.9+ deprecation of collections members

This fix is part of a larger error handling cleanup.
Py3 generates deprecation warnings of access to containers.Iterator (etc) and states they will break in py3.9. Commit prefers to access members via collections.abs if py3, with a fallback for older py2 location.

Refs go-python/gopy #254

Author: justinfx

bind/gen.go

@@ -226,6 +226,11 @@ mod.add_function('NumHandles', retval('int'), [])
 
 # the following is required to enable dlopen to open the _go.so file
 import os,sys,inspect,collections
+try:
+	import collections.abc as _collections_abc
+except ImportError:
+	_collections_abc = collections
+
 cwd = os.getcwd()
 currentdir = os.path.dirname(os.path.abspath(inspect.getfile(inspect.currentframe())))
 os.chdir(currentdir)
@@ -250,6 +255,10 @@ os.chdir(cwd)
 # %[2]s
 
 import collections
+try:
+	import collections.abc as _collections_abc
+except ImportError:
+	_collections_abc = collections
 %[6]s
 
 # to use this code in your end-user python file, import it as follows:
@@ -263,6 +272,10 @@ import collections
 
 	GoPkgDefs = `
 import collections
+try:
+	import collections.abc as _collections_abc
+except ImportError:
+	_collections_abc = collections
 	
 class GoClass(object):
 	"""GoClass is the base class for all GoPy wrapper classes"""

bind/gen_map.go

@@ -112,7 +112,7 @@ otherwise parameter is a python list that we copy from
 		g.pywrap.Printf("_%s.IncRef(self.handle)\n", g.pypkgname)
 		g.pywrap.Printf("if len(args) > 0:\n")
 		g.pywrap.Indent()
-		g.pywrap.Printf("if not isinstance(args[0], collections.Mapping):\n")
+		g.pywrap.Printf("if not isinstance(args[0], _collections_abc.Mapping):\n")
 		g.pywrap.Indent()
 		g.pywrap.Printf("raise TypeError('%s.__init__ takes a mapping as argument')\n", slNm)
 		g.pywrap.Outdent()

bind/gen_slice.go

@@ -106,7 +106,7 @@ otherwise parameter is a python list that we copy from
 			g.pywrap.Printf("_%s.IncRef(self.handle)\n", g.pypkgname)
 			g.pywrap.Printf("if len(args) > 0:\n")
 			g.pywrap.Indent()
-			g.pywrap.Printf("if not isinstance(args[0], collections.Iterable):\n")
+			g.pywrap.Printf("if not isinstance(args[0], _collections_abc.Iterable):\n")
 			g.pywrap.Indent()
 			g.pywrap.Printf("raise TypeError('%s.__init__ takes a sequence as argument')\n", slNm)
 			g.pywrap.Outdent()
@@ -220,7 +220,7 @@ otherwise parameter is a python list that we copy from
 		if slc.isSlice() {
 			g.pywrap.Printf("def __iadd__(self, value):\n")
 			g.pywrap.Indent()
-			g.pywrap.Printf("if not isinstance(value, collections.Iterable):\n")
+			g.pywrap.Printf("if not isinstance(value, _collections_abc.Iterable):\n")
 			g.pywrap.Indent()
 			g.pywrap.Printf("raise TypeError('%s.__iadd__ takes a sequence as argument')\n", slNm)
 			g.pywrap.Outdent()