Make a new urllib package .

It consists of code from urllib, urllib2, urlparse, and robotparser.
The old modules have all been removed.  The new package has five
submodules: urllib.parse, urllib.request, urllib.response,
urllib.error, and urllib.robotparser.  The urllib.request.urlopen()
function uses the url opener from urllib2.

Note that the unittests have not been renamed for the
beta, but they will be renamed in the future.

Joint work with Senthil Kumaran.
diff --git a/Lib/urllib/error.py b/Lib/urllib/error.py
new file mode 100644
index 0000000..300c3fe
--- /dev/null
+++ b/Lib/urllib/error.py
@@ -0,0 +1,59 @@
+"""Exception classes raised by urllib.
+
+The base exception class is URLError, which inherits from IOError.  It
+doesn't define any behavior of its own, but is the base class for all
+exceptions defined in this package.
+
+HTTPError is an exception class that is also a valid HTTP response
+instance.  It behaves this way because HTTP protocol errors are valid
+responses, with a status code, headers, and a body.  In some contexts,
+an application may want to handle an exception like a regular
+response.
+"""
+
+import urllib.response
+
+# do these error classes make sense?
+# make sure all of the IOError stuff is overridden.  we just want to be
+# subtypes.
+
+class URLError(IOError):
+    # URLError is a sub-type of IOError, but it doesn't share any of
+    # the implementation.  need to override __init__ and __str__.
+    # It sets self.args for compatibility with other EnvironmentError
+    # subclasses, but args doesn't have the typical format with errno in
+    # slot 0 and strerror in slot 1.  This may be better than nothing.
+    def __init__(self, reason, filename=None):
+        self.args = reason,
+        self.reason = reason
+        if filename is not None:
+            self.filename = filename
+
+    def __str__(self):
+        return '<urlopen error %s>' % self.reason
+
+class HTTPError(URLError, urllib.response.addinfourl):
+    """Raised when HTTP error occurs, but also acts like non-error return"""
+    __super_init = urllib.response.addinfourl.__init__
+
+    def __init__(self, url, code, msg, hdrs, fp):
+        self.code = code
+        self.msg = msg
+        self.hdrs = hdrs
+        self.fp = fp
+        self.filename = url
+        # The addinfourl classes depend on fp being a valid file
+        # object.  In some cases, the HTTPError may not have a valid
+        # file object.  If this happens, the simplest workaround is to
+        # not initialize the base classes.
+        if fp is not None:
+            self.__super_init(fp, hdrs, url, code)
+
+    def __str__(self):
+        return 'HTTP Error %s: %s' % (self.code, self.msg)
+
+# exception raised when downloaded size does not match content-length
+class ContentTooShortError(URLError):
+    def __init__(self, message, content):
+        URLError.__init__(self, message)
+        self.content = content