bugfix: ValueError: underlying buffer has been detached (erikrose#129)

Prevent error condition, ValueError: underlying buffer has been detached from raising, Closes erikrose#126

blessed/terminal.py

@@ -175,7 +175,9 @@ def __init__(self, kind=None, stream=None, force_styling=False):
         try:
             stream_fd = (stream.fileno() if hasattr(stream, 'fileno') and
                          callable(stream.fileno) else None)
-        except io.UnsupportedOperation:
+        except (io.UnsupportedOperation, ValueError):
+            # The stream is not a file, such as the case of StringIO, or, when it has been
+            # "detached", such as might be the case of stdout in some test scenarios.
             stream_fd = None
 
         self._stream = stream

docs/history.rst

@@ -4,6 +4,8 @@ Version History
   * introduced: 24-bit color support, detected by ``term.number_of_colors == 1 << 24``,
     and 24-bit color foreground method :meth:`~Terminal.color_rgb` and background method
     :meth:`~Terminal.on_color_rgb`.
+  * bugfix: prevent error condition, ``ValueError: underlying buffer has been detached`` in rare
+    conditions where sys.__stdout__ has been detached in test frameworks. :ghissue:`126`.
   * bugfix: off-by-one error in :meth:`~.Terminal.get_location`, now accounts for
     ``%i`` in cursor_report, :ghissue:`94`.
   * bugfix :meth:`~Terminal.split_seqs` and related functions failed to match when the