IOStream: Ignore missing attrs from `dir()`. #6386

In some cases calling `getattr()` on attributes found with
`dir()` will fail. This is seen in Issue  #6386.

The attribute in that issue is `name`, which is not needed for
`IOStream` to work correctly. This fix will set the attribute
to `None` and move on.

Tests were added in `IPython.utils.tests.test_io.py` to catch
any regressions.

IPython/utils/io.py

@@ -37,7 +37,12 b' class IOStream:'
         def clone(meth):
             return not hasattr(self, meth) and not meth.startswith('_')
         for meth in filter(clone, dir(stream)):
-            setattr(self, meth, getattr(stream, meth))
+            try:
+                val = getattr(stream, meth)
+            except AttributeError:
+                pass
+            else:
+                setattr(self, meth, val)
 
     def __repr__(self):
         cls = self.__class__

IPython/utils/tests/test_io.py

@@ -17,7 +17,7 b' import unittest'
 import nose.tools as nt
 
 from IPython.testing.decorators import skipif, skip_win32
-from IPython.utils.io import Tee, capture_output
+from IPython.utils.io import IOStream, Tee, capture_output
 from IPython.utils.py3compat import doctest_refactor_print
 from IPython.utils.tempdir import TemporaryDirectory
 
@@ -68,6 +68,19 b' def test_io_init():'
         # just test for string equality.
         assert 'IPython.utils.io.IOStream' in classname, classname
 
+def test_IOStream_init():
+    """IOStream initializes from a file-like object missing attributes. """
+    # Cause a failure from getattr and dir(). (Issue #6386)
+    class BadStringIO(StringIO):
+        def __dir__(self):
+            attrs = super(StringIO, self).__dir__()
+            attrs.append('name')
+            return attrs
+
+    iostream = IOStream(BadStringIO())
+    iostream.write('hi, bad iostream\n')
+    assert not hasattr(iostream, 'name')
+
 def test_capture_output():
     """capture_output() context works"""