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In maintenance (ie. when doing a big update), the links displayed in piwik do not work, as they use the proxy which is in maintenance too ;-)
So, we could either enable proxy during maintenance, or change the links to not set the proxy.
This was reported in: http://forum.piwik.org/read.php?2,93851
Reproduce: Enable maintenance as per doc: http://piwik.org/faq/how-to/#faq_111
Click on link.
Solution: the links should be to piwik.org directly in the error message rather than go through proxy.
(In ) Fixes #3384, link directly to piwik.org in exception message.