It seems that urllib2 changes the writing of any
additional supplied headers, i.e. "User-Agent" becomes
"User-agent", "TEST-HEADER" becomes "Test-header".

A few sites do not recognize "User-agent" and insist on
"User-Agent".

Fix: remove all occurences of capitalize() in urllib2.

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There are old, closed Bug-Reports:
https://sourceforge.net/tracker/?group_id=5470&atid=105470&func=detail&aid=994101

?!?!?

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Some normalizing is important to prevent duplicate headers.
Changed capitalize() to title() to match the default casing
(now user-agent becomes User-Agent) in rev. 43399.

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I checked the database before submitting...  I admit, I
haven't gone back 2 years. :-)

It seems to be the same bug. But it was still present in
2.4.2 (version used in Ubuntu Breezy).

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Patch 1459963 (applied in 50842) should be reverted and a
better patch applied (see below), since this one needlessly
breaks the old (albeit undocumented) interface of direct
access to request.headers (which existed prior to the
introduction of the .get_header() &c. methods).

Patch 1542948 reverts 50842's changes to urllib2 (it does
not revert the changes to urllib) and fixes the reported
issue with a one-line fix in AbstractHTTPHandler
(.title()-case the HTTP headers before sending them to
httplib). That fix is also more localised to HTTP -- urllib2
knows about other protocols too. This patch also corrects a
mis-wording in Misc/NEWS: the old case convention was not
strictly incorrect (according to RFC 2616), but just did not
follow the usual title-case convention.

If the original patch was applied to the 2.4 maintenance
branch, I guess patch 1542948 should be applied there too.

(Just BTW: With hindsight, the methods should never have
been introduced (which was done when the "unredirected"
headers were introduced), but rather request.headers changed
to be a class != dict: that was my fault, and it's too late
to fix that...)