Do not clutter terminal when showing traceback

tools/testein.py

@@ -4,9 +4,11 @@
 Run EIN test suite
 """
 
+import sys
 import os
 import glob
 from subprocess import Popen, PIPE, STDOUT
+import itertools
 
 EIN_ROOT = os.path.normpath(
     os.path.join(os.path.dirname(__file__), os.path.pardir))
@@ -40,6 +42,45 @@ def einlibdir(*path):
     return eindir('lib', *path)
 
 
+def show_nonprinting(string, stream=sys.stdout):
+    """Emulate ``cat -v`` (``--show-nonprinting``)."""
+    stream.writelines(itertools.imap(chr, convert_nonprinting(string)))
+
+
+def convert_nonprinting(string):
+    """
+    Convert non-printing characters in `string`.
+
+    Output is iterable of int.  So for Python 2, you need to
+    convert it into string using `chr`.
+
+    Adapted from: http://stackoverflow.com/a/437542/727827
+
+    """
+
+    for b in itertools.imap(ord, string):
+        assert 0 <= b < 0x100
+
+        if b in (0x09, 0x0a):   # '\t\n'
+            yield b
+            continue
+
+        if b > 0x7f:            # not ascii
+            yield 0x4d          # 'M'
+            yield 0x2d          # '-'
+            b &= 0x7f
+
+        if b < 0x20:            # control char
+            yield 0x5e          # '^'
+            b |= 0x40
+        elif b == 0x7f:
+            yield 0x5e          # '^'
+            yield 0x3f          # '?'
+            continue
+
+        yield b
+
+
 class BaseRunner(object):
 
     def __init__(self, **kwds):
@@ -177,7 +218,7 @@ class TestRunner(BaseRunner):
             print
             print "*" * 50
             print "Showing STDOUT/STDERR:"
-            print stdout
+            show_nonprinting(stdout)
             print
             print "{0} failed".format(self.testfile)
         else: