If eg. ~/.Xauthority is unreadable, X will spew "No protocol specified" error, but the error is singularly uninformative, and the cause cannot be found in log files either. I had to resort to strace to find out what it wanted.
Assigning to Xlib component, since those messages (which are admittedly confusing and need help) come from XOpenDisplay() in libX11.
*** Bug 36429 has been marked as a duplicate of this bug. ***
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