Issue #16714: use 'raise' exceptions, don't 'throw'.

Patch by Serhiy Storchaka.
diff --git a/Lib/io.py b/Lib/io.py
index 57e6e0d..2283276 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -4,7 +4,7 @@
 At the top of the I/O hierarchy is the abstract base class IOBase. It
 defines the basic interface to a stream. Note, however, that there is no
 separation between reading and writing to streams; implementations are
-allowed to throw an IOError if they do not support a given operation.
+allowed to raise an IOError if they do not support a given operation.
 
 Extending IOBase is RawIOBase which deals simply with the reading and
 writing of raw bytes to a stream. FileIO subclasses RawIOBase to provide