Encode layer output if needed as UTF-8 before writing it to a buffer …

…that explicitly (only) accepts bytes.

Update the test case to make this explicit. There are three test failures without doing the encoding.

Fixes #80

CHANGES.rst

@@ -5,7 +5,9 @@
 4.9.2 (unreleased)
 ==================
 
-- Nothing changed yet.
+- Fix ``TypeError: a bytes-like object is required, not 'str'``
+  running tests in parallel on Python 3. See `issue 80
+  <https://github.com/zopefoundation/zope.testrunner/issues/80>`_.
 
 
 4.9.1 (2018-11-21)

src/zope/testrunner/runner.py

@@ -697,6 +697,7 @@ def resume_tests(script_parts, options, features, layers, failures, errors,
     current_result = next(results_iter)
     last_layer_intermediate_output = None
     output = None
+    # Get an object that (only) accepts bytes
     stdout = _get_output_buffer(sys.stdout)
     while ready_threads or running_threads:
         while len(running_threads) < options.processes and ready_threads:
@@ -723,6 +724,8 @@ def resume_tests(script_parts, options, features, layers, failures, errors,
                     ('[Parallel tests running in '
                      '%s:\n  ' % (layer_name,)).encode('utf-8'))
                 last_layer_intermediate_output = layer_name
+            if not isinstance(output, bytes):
+                output = output.encode('utf-8')
             stdout.write(output)
         # Display results in the order they would have been displayed, had the
         # work not been done in parallel.

src/zope/testrunner/tests/testrunner-layers-buff.rst

@@ -9,15 +9,32 @@ First, we wrap stdout with an object that instruments it. It notes the time at
 which a given line was written.
 
     >>> import os, sys, datetime
-    >>> class RecordingStreamWrapper:
+    >>> class RecordingStreamWrapper(object):
     ...     def __init__(self, wrapped):
     ...         self.record = []
     ...         self.wrapped = wrapped
+    ...     @property
+    ...     def buffer(self):
+    ...         # runner._get_output_buffer attempts to write b''
+    ...         # to us, and when that fails (see write()), accesses our .buffer directly.
+    ...         # That object deals in bytes.
+    ...         wrapper = self
+    ...         class buffer(object):
+    ...             def write(self, data):
+    ...                  assert isinstance(data, bytes)
+    ...                  wrapper.write(data.decode('utf-8'))
+    ...             def writelines(self, lines):
+    ...                  for line in lines:
+    ...                      self.write(line)
+    ...             def flush(self):
+    ...                  wrapper.flush()
+    ...         return buffer()
     ...     def write(self, out):
-    ...         # Not very accurate, but it will do as long as we don't
-    ...         # actually need to be binary-clean.
+    ...         # sys.stdout deals with native strings;
+    ...         # and raises TypeError for other things. We must do
+    ...         # the same.
     ...         if not isinstance(out, str):
-    ...             out = out.decode('utf-8')
+    ...              raise TypeError
     ...         self.record.append((out, datetime.datetime.now()))
     ...         self.wrapped.write(out)
     ...     def writelines(self, lines):
@@ -80,7 +97,7 @@ more than a second after the second suite ran.
     ...         if time-last_time >= pause:
     ...             # We paused!
     ...             print('PAUSE FOUND BETWEEN THESE LINES:')
-    ...             print(''.join([last_line, line, '-'*70]))
+    ...             print(''.join([last_line, line, '-' * 70]))
     ...         last_line, last_time = line, time
 
     >>> assert_progressive_output() # doctest: +ELLIPSIS