Add documentation for doctest flags and remove dead code

CHANGELOG

@@ -1,6 +1,8 @@
 Unreleased
 ----------
 
+- add a doctest option for doctest flags
+
 - Improve assertion failure reporting on iterables, by using ndiff and pprint.
 
 - removed outdated japanese docs from source tree.

_pytest/doctest.py

@@ -102,9 +102,6 @@ def get_optionflags(parent):
     import doctest
     optionflags_str = parent.config.getini("doctest_optionflags")
     flag_lookup_table = _get_flag_lookup()
-    if not optionflags_str:
-        return doctest.ELLIPSIS
-
     flag_acc = 0
     for flag in optionflags_str:
         flag_acc |= flag_lookup_table[flag]

doc/en/customize.txt

@@ -126,3 +126,8 @@ Builtin configuration file options
    derived class.
 
    See :ref:`change naming conventions` for examples.
+
+.. confval:: doctest_optionflags
+
+   One or more doctest flag names from the standard ``doctest`` module.
+   `See how py.test handles doctests <doctest.html>`_.

doc/en/doctest.txt

@@ -60,3 +60,12 @@ It is possible to use fixtures using the ``getfixture`` helper::
 
 Also, :ref:`usefixtures` and :ref:`autouse` fixtures are supported
 when executing text doctest files.
+
+The standard ``doctest`` module provides some setting flags to configure the
+strictness of doctest tests. In py.test You can enable those flags those flags
+using the configuration file. To make pytest ignore trailing whitespaces and
+ignore lengthy exception stack traces you can just write::
+
+    # content of pytest.ini
+    [pytest]
+    doctest_optionflags= NORMALIZE_WHITESPACE IGNORE_EXCEPTION_DETAIL