Thinking about it a bit more, what'd be really nice to have is a way to validate .qbk files that could be invoked from Travis/Appveyor, so that we can run that in PRs. But the problem here is that this validator would ideally be written in Python, so as to not require building Quickbook.
On second thought, the idea of rewriting Quickbook in Python is a bit stupid. There is a prebuilt Quickbook in libboost-dev, but it's 1.46 on Ubuntu Precise which Travis uses, so it will not contain our hypothetical strict validation options. We could bite the bullet and build it from source, I suppose. But... D:\tmp2\boost>python2.7.exe tools/boostdep/depinst/depinst.py ../tools/quickbook Installing module core Installing module preprocessor Installing module iterator Installing module algorithm Installing module tuple Installing module bind Installing module smart_ptr Installing module unordered Installing module assert Installing module range Installing module program_options Installing module foreach Installing module filesystem Installing module lexical_cast Installing module config Installing module spirit Installing module iostreams Installing module utility Installing module locale Installing module move Installing module functional Installing module system Installing module tti Installing module concept_check Installing module io Installing module integer Installing module array Installing module regex Installing module static_assert Installing module container Installing module predef Installing module proto Installing module detail Installing module any Installing module type_traits Installing module numeric/conversion Installing module function Installing module tokenizer Installing module random Installing module phoenix Installing module mpl Installing module endian Installing module variant Installing module conversion Installing module fusion Installing module serialization Installing module optional Installing module pool Installing module function_types Installing module exception Installing module thread Installing module typeof Installing module math Installing module throw_exception Installing module type_index Installing module atomic Installing module intrusive Installing module winapi Installing module date_time Installing module chrono Installing module lambda Installing module ratio Installing module rational Hmm. :-)