Mention that binary packages cannot be patched in auto doc introduction

- changed version for auto doc to 3.2
- removed unused test code
diff --git a/docs/conf.py b/docs/conf.py
index b6a14a4..998c576 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -63,9 +63,9 @@
 # built documents.
 #
 # The short X.Y version.
-version = '3.1'
+version = '3.2'
 # The full version, including alpha/beta/rc tags.
-release = '3.1'
+release = '3.2'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
diff --git a/docs/intro.rst b/docs/intro.rst
index 12d191d..acb5add 100644
--- a/docs/intro.rst
+++ b/docs/intro.rst
@@ -5,6 +5,9 @@
 Using pyfakefs, your tests operate on a fake file system in memory without touching the real disk.
 The software under test requires no modification to work with pyfakefs.
 
+Note that pyfakefs will not work with Python libraries that use C libraries to access the
+file system, because it cannot patch the underlying C libraries' file access functions.
+
 pyfakefs works with Python 2.6 and above, on Linux, Windows and MacOS.
 
 pyfakefs works with `PyTest <doc.pytest.org>`__ version 2.8.6 or above.