Backporting CDRIVER-1013 from the master branch (where 1.3 development is in progress) to the r1.2 branch, I naively copied the entire CMakeLists.txt. This included the desired changes for parsing version numbers from config files, but it also included unintentional changes that referenced source files only present on the master branch, not in r1.2.

The error from cmake is:

CMake Error at CMakeLists.txt:219 (add_library):
  Cannot find source file:

    /Users/emptysquare/.virtualenvs/c-driver/mongo-c-driver/src/mongoc/mongoc-find-and-modify.c