Update stdin_get_value monkey-patching

Let's use an enclosed function to replace the stdin_get_value function
on pep8.

Closes #107

CHANGES.rst

@@ -1,13 +1,19 @@
 CHANGES
 =======
 
-2.x.y - 2015-aa-bb
+2.5.1 - 2015-12-15
 ------------------
 
 - **Bug** Properly look for ``.flake8`` in current working directory
   (`GitLab#103`_)
 
+- **Bug** Monkey-patch ``pep8.stdin_get_value`` to cache the actual value in
+  stdin. This helps plugins relying on the function when run with
+  multiprocessing. (`GitLab#105`_, `GitLab#107`_)
+
 .. _GitLab#103: https://gitlab.com/pycqa/flake8/issues/103
+.. _GitLab#105: https://gitlab.com/pycqa/flake8/issues/105
+.. _GitLab#107: https://gitlab.com/pycqa/flake8/issues/107
 
 2.5.0 - 2015-10-26
 ------------------

flake8/engine.py

@@ -297,13 +297,20 @@ def get_python_version():
     return '%s%s on %s' % (impl, platform.python_version(), platform.system())
 
 
-def make_stdin_get_value():
+def make_stdin_get_value(original):
-    value = pep8.stdin_get_value()
+    def stdin_get_value():
-    if sys.version_info < (3, 0):
+        if not hasattr(stdin_get_value, 'cached_stdin'):
-        stdin = io.BytesIO(value)
+            value = original()
-    else:
+            if sys.version_info < (3, 0):
-        stdin = io.StringIO(value)
+                stdin = io.BytesIO(value)
-    return stdin.getvalue
+            else:
+                stdin = io.StringIO(value)
+            stdin_get_value.cached_stdin = stdin
+        else:
+            stdin = stdin_get_value.cached_stdin
+        return stdin.getvalue()
+
+    return stdin_get_value
 
 
-pep8.stdin_get_value = make_stdin_get_value()
+pep8.stdin_get_value = make_stdin_get_value(pep8.stdin_get_value)