Patch #602345 by Neal Norwitz and me: add -B option and PYTHONDONTWRITEBYTECODE envvar to skip writing bytecode.
diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index 24ce207..a98c5d4 100644
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -507,6 +507,17 @@
    when Python is started with the -3 option.
 
 
+.. data:: dont_write_bytecode
+
+   If this is true, Python won't try to write ``.pyc`` or ``.pyo`` files on the
+   import of source modules.  This value is initially set to ``True`` or ``False``
+   depending on the ``-B`` command line option and the ``PYTHONDONTWRITEBYTECODE``
+   environment variable, but you can set it yourself to control bytecode file
+   generation.
+
+   .. versionadded:: 2.6
+
+
 .. function:: setcheckinterval(interval)
 
    Set the interpreter's "check interval".  This integer value determines how often