patches/pylint: fix regression with namedtuples

with namedtuples and unicode literals enabled, our patch break with:

  Module py2stdlib, line 266, in infer_named_tuple
    ''' % {'name': name, 'fields': attributes})
  Module Products.ERP5Type.patches.pylint, line 74, in string_build
    encoding = _guess_encoding(data)
  Module astroid.builder, line 65, in _guess_encoding
    if string.startswith('\xef\xbb\xbf'):
UnicodeDecodeError: 'ascii' codec can't decode byte 0xef in position 0: ordinal not in range(128)

product/ERP5Type/patches/pylint.py

@@ -70,6 +70,11 @@ def string_build(self, data, modname='', path=None):
       module.file_bytes = data.encode('utf-8')
       return self._post_build(module, 'utf-8')
     """
+    if isinstance(data, unicode):
+	# When called internally by pylint/astroid and if the source code imports
+	# `unicode_literals`, the source code may end up being an unicode object
+	# (example: `infer_named_tuple()`)
+        data = data.encode('utf-8')
     encoding = _guess_encoding(data)
     if encoding is None:
         # Encoding not defined in the source file, assuming utf-8...

product/ERP5Type/tests/testDynamicClassGeneration.py

@@ -2308,6 +2308,20 @@ undefined()
        imported_module2_with_version])
     self.assertEqual(component.getTextContentWarningMessageList(), [])
 
+  def testPylintNamedtupleUnicodeLiteralsRegression(self):
+    # regression for a bug with our pylint patches on guess encoding
+    # a named tuple with unicode_literals enabled cause UnicodeDecodeError
+    component = self._newComponent(
+        self._generateReference('TestPylintNamedtupleUnicodeLiteralsRegression'))
+    component.setTextContent("""
+from __future__ import unicode_literals
+from collections import namedtuple
+namedtuple('NamedTuple', 'foo bar')(1, 2)
+""")
+    self.tic()
+    self.assertEqual(component.getTextContentWarningMessageList(), [])
+    self.assertEqual(component.getTextContentErrorMessageList(), [])
+
 from Products.ERP5Type.Core.ExtensionComponent import ExtensionComponent
 
 class TestZodbExtensionComponent(_TestZodbComponent):