Print filenames that doesn't comply PEP8

The old output was missing filenames, e.g.

    AssertionError: Found PEP8 errors that may break your code in Python 3:
    2       E201 whitespace after '['
    3       E202 whitespace before ']'
    2       E203 whitespace before ':'
    1       E221 multiple spaces before operator
    1       E302 expected 2 blank lines, found 1
    2       E303 too many blank lines (2)

That's now usefull at all. Where the heck should I search for these errors. The
new output is a little bit messy but contains more usefull information, e.g.

    AssertionError: Found PEP8 errors that may break your code in Python 3:
    /tito/test/unit/../../src/tito/release/LocalYumRepo.py:9:1: E302 expected 2 blank lines, found 1
    /tito/test/unit/../../src/tito/release/LocalYumRepo.py:17:66: E202 whitespace before ']'
    /tito/test/unit/../../src/tito/release/LocalYumRepo.py:21:15: E203 whitespace before ':'
    /tito/test/unit/../../src/tito/release/LocalYumRepo.py:22:16: E203 whitespace before ':'
    /tito/test/unit/../../src/tito/release/LocalYumRepo.py:26:18: E201 whitespace after '['
    /tito/test/unit/../../src/tito/release/LocalYumRepo.py:26:32: E202 whitespace before ']'
    /tito/test/unit/../../src/tito/release/LocalYumRepo.py:29:15: E201 whitespace after '['
    /tito/test/unit/../../src/tito/release/LocalYumRepo.py:29:32: E202 whitespace before ']'
    /tito/test/unit/../../src/tito/release/LocalYumRepo.py:35:17: E221 multiple spaces before operator
    /tito/test/unit/../../src/tito/release/LocalYumRepo.py:76:5: E303 too many blank lines (2)

src/tito/compat.py

@@ -18,6 +18,7 @@ Compatibility library for Python 2.4 up through Python 3.
 """
 import os
 import sys
+import contextlib
 ENCODING = sys.getdefaultencoding()
 PY2 = sys.version_info[0] == 2
 if PY2:
@@ -35,6 +36,7 @@ else:
     from configparser import RawConfigParser
     from io import StringIO
     from urllib.parse import urlparse
+    from contextlib import redirect_stdout
     import xmlrpc.client as xmlrpclib
     text_type = str
     binary_type = bytes
@@ -98,3 +100,14 @@ def write(fd, str):
         os.write(fd, str)
     else:
         os.write(fd, bytes(str, ENCODING))
+
+
+if PY2:
+    @contextlib.contextmanager
+    def redirect_stdout(target):
+        original = sys.stdout
+        try:
+            sys.stdout = target
+            yield
+        finally:
+            sys.stdout = original

test/unit/pep8_tests.py

@@ -31,6 +31,7 @@ except ImportError:
 
 
 from tito.compat import *  # NOQA
+from tito.compat import StringIO, redirect_stdout
 from unit.fixture import TitoUnitTestFixture, REPO_DIR
 
 
@@ -66,9 +67,15 @@ class TestPep8(TitoUnitTestFixture):
 
         try:
             checker = pep8.StyleGuide(select=tests, paths=[REPO_DIR], reporter=pep8.StandardReport)
-            report = checker.check_files()
-            result = report.total_errors
-            output = "\n".join(report.get_statistics())
+            # Unfortunatelly, IMHO the most interesting information
+            # `checker.check_files()` prints to the STDOUT and doesn't provide
+            # API to get it - the list of _bad_ files. Let's just read it from
+            # the output
+            with StringIO() as buf, redirect_stdout(buf):
+                report = checker.check_files()
+                result = report.total_errors
+                output = buf.getvalue()
+
         except AttributeError:
             # We don't have pep8.StyleGuide, so we must be
             # using pep8 older than git tag 1.1-72-gf20d656.