Travis provides a "3.8-dev" python, which is updated regularly to track cpython master. When running our tests on this Python, specifically version

  python: 3.8.0a0 (heads/master:f75d59e, Feb  3 2019, 07:27:24) 

we just started getting tracebacks:

  TypeError                                 Traceback (most recent call last)
  /opt/python/3.8-dev/lib/python3.8/codeop.py in __call__(self, source, filename, symbol)
      131 
      132     def __call__(self, source, filename, symbol):
  --> 133         codeob = compile(source, filename, symbol, self.flags, 1)
      134         for feature in _features:
      135             if codeob.co_flags & feature.compiler_flag:
  TypeError: required field "type_ignores" missing from Module

(Full log: https://travis-ci.org/python-trio/trio/jobs/488312057)

Grepping through git diffs for 'type_ignores' suggests that this is probably related to bpo-35766.

I haven't dug into this in detail, but it seems to be happening on tests using IPython. The lack of further traceback suggests to me that the exception is happening inside IPython's guts (it has some hacks to try to figure out which parts of the traceback are in user-defined code versus its own internal code, and tries to hide the latter when printing tracebacks). The crash is in codeop.Compile.__call__, and IPython does create ast.Module objects and pass them to codeop.Compile.__call__:

https://github.com/ipython/ipython/blob/512d47340c09d184e20811ca46aaa2f862bcbafe/IPython/core/interactiveshell.py#L3199-L3200

Maybe ast.Module needs to default-initialize the new type_ignores field, or compile() needs to be tolerant of it being missing?