New thing to me, but according to people.debian.org/~mlang/a11y/software.en.html there is something:
Recite is a program to do speech synthesis. The quality of sound produced is not terribly good, but it should be adequate for reporting the occasional error message verbally.
Given some English text, recite will convert it to a series of phonemes, then convert the phonemes to a sequence of vocal tract parameters, and then synthesis the sound a vocal tract would make to say the sentence. Recite can perform a subset of these operations, so it can be used to convert text into phonemes, or to produce an utterance based on vocal tract parameters computed by another program.
A quick web search told, among that, that such software doesn't exist too widely. Try that out if you will..