Python 3.7 support - deprecation of classes in the collections module

Change the base classes in the pyabc.i file to use the
collections.abc module instead of collections due to the deprecation
of the classes in the collections module in Python 3.7.

Examples/test-suite/python/python_abstractbase_runme3.py

@@ -1,5 +1,11 @@
+import sys
+
+# collections.abc requires Python 3.3+
+if sys.version_info[0:2] < (3, 3):
+    exit(0)
+
 from python_abstractbase import *
-from collections import *
+import collections.abc
 
 # This is expected to fail with -builtin option
 # Builtin types can't inherit from pure-python abstract bases
@@ -10,12 +16,16 @@ if is_python_builtin():
 if not is_swig_py3:
     exit(0)
 
-assert issubclass(Mapii, MutableMapping)
-assert issubclass(Multimapii, MutableMapping)
-assert issubclass(IntSet, MutableSet)
-assert issubclass(IntMultiset, MutableSet)
-assert issubclass(IntVector, MutableSequence)
-assert issubclass(IntList, MutableSequence)
+def check_issubclass(derived, base):
+    if not issubclass(derived, base):
+        raise RuntimeError("{} is not a subclass of {}".format(derived, base))
+
+check_issubclass(Mapii, collections.abc.MutableMapping)
+check_issubclass(Multimapii, collections.abc.MutableMapping)
+check_issubclass(IntSet, collections.abc.MutableSet)
+check_issubclass(IntMultiset, collections.abc.MutableSet)
+check_issubclass(IntVector, collections.abc.MutableSequence)
+check_issubclass(IntList, collections.abc.MutableSequence)
 
 mapii = Mapii()
 multimapii = Multimapii()