Get 'py35-pure' tox environment passing.

On Py3k, the conditional imports fail with an AttributeError when the
C extensions are missing, rather than an ImportError.

BTrees/IFBTree.py

@@ -106,7 +106,7 @@ class IFTreeIteratorPy(_TreeIterator):
 
 try:
     from ._IFBTree import IFBucket
-except ImportError: #pragma NO COVER w/ C extensions
+except (ImportError, AttributeError): #pragma NO COVER w/ C extensions
     IFBucket = IFBucketPy
     IFSet = IFSetPy
     IFBTree = IFBTreePy

BTrees/IIBTree.py

@@ -107,7 +107,7 @@ class IITreeIteratorPy(_TreeIterator):
 
 try:
     from ._IIBTree import IIBucket
-except ImportError: #pragma NO COVER w/ C extensions
+except (ImportError, AttributeError): #pragma NO COVER w/ C extensions
     IIBucket = IIBucketPy
     IISet = IISetPy
     IIBTree = IIBTreePy

BTrees/IOBTree.py

@@ -89,7 +89,7 @@ class IOTreeIteratorPy(_TreeIterator):
 
 try:
     from ._IOBTree import IOBucket
-except ImportError: #pragma NO COVER w/ C extensions
+except (ImportError, AttributeError): #pragma NO COVER w/ C extensions
     IOBucket = IOBucketPy
     IOSet = IOSetPy
     IOBTree = IOBTreePy

BTrees/LFBTree.py

@@ -107,7 +107,7 @@ class LFTreeIteratorPy(_TreeIterator):
 
 try:
     from ._LFBTree import LFBucket
-except ImportError: #pragma NO COVER w/ C extensions
+except (ImportError, AttributeError): #pragma NO COVER w/ C extensions
     LFBucket = LFBucketPy
     LFSet = LFSetPy
     LFBTree = LFBTreePy

BTrees/LLBTree.py

@@ -107,7 +107,7 @@ class LLTreeIteratorPy(_TreeIterator):
 
 try:
     from ._LLBTree import LLBucket
-except ImportError: #pragma NO COVER w/ C extensions
+except (ImportError, AttributeError): #pragma NO COVER w/ C extensions
     LLBucket = LLBucketPy
     LLSet = LLSetPy
     LLBTree = LLBTreePy

BTrees/LOBTree.py

@@ -90,7 +90,7 @@ class LOTreeIteratorPy(_TreeIterator):
 
 try:
     from ._LOBTree import LOBucket
-except ImportError: #pragma NO COVER w/ C extensions
+except (ImportError, AttributeError): #pragma NO COVER w/ C extensions
     LOBucket = LOBucketPy
     LOSet = LOSetPy
     LOBTree = LOBTreePy

BTrees/OIBTree.py

@@ -104,7 +104,7 @@ class OITreeIteratorPy(_TreeIterator):
 
 try:
     from ._OIBTree import OIBucket
-except ImportError: #pragma NO COVER w/ C extensions
+except (ImportError, AttributeError): #pragma NO COVER w/ C extensions
     OIBucket = OIBucketPy
     OISet = OISetPy
     OIBTree = OIBTreePy

BTrees/OLBTree.py

@@ -105,7 +105,7 @@ class OLTreeIteratorPy(_TreeIterator):
 
 try:
     from ._OLBTree import OLBucket
-except ImportError: #pragma NO COVER w/ C extensions
+except (ImportError, AttributeError): #pragma NO COVER w/ C extensions
     OLBucket = OLBucketPy
     OLSet = OLSetPy
     OLBTree = OLBTreePy

BTrees/OOBTree.py

@@ -85,7 +85,7 @@ class OOTreeIteratorPy(_TreeIterator):
 
 try:
     from ._OOBTree import OOBucket
-except ImportError as e: #pragma NO COVER w/ C extensions
+except (ImportError, AttributeError): #pragma NO COVER w/ C extensions
     OOBucket = OOBucketPy
     OOSet = OOSetPy
     OOBTree = OOBTreePy

BTrees/_base.py

@@ -49,7 +49,7 @@ def __init__(self, items=None):
         # If the C extensions are around, we do need these methods, but
         # these classes are unlikely to be used in production anyway.
         __import__('BTrees._OOBTree')
-    except ImportError:  # pragma: no cover
+    except (ImportError, AttributeError):  # pragma: no cover
         pass
     else:
         def __reduce__(self):

BTrees/fsBTree.py

@@ -103,7 +103,7 @@ class fsTreeSetPy(TreeSet):
 
 try:
     from ._fsBTree import fsBucket
-except ImportError: #pragma NO COVER w/ C extensions
+except (ImportError, AttributeError): #pragma NO COVER w/ C extensions
     fsBucket = fsBucketPy
     fsSet = fsSetPy
     fsBTree = fsBTreePy