tests: Ignore exception chain test on the WiPy.

Fails because warnings are not enabled on the CC3200.

tests/run-tests

@@ -197,6 +197,7 @@ def run_tests(pyb, tests, args):
             skip_tests.add('extmod/zlibd_decompress.py')    # requires zlib
             skip_tests.add('extmod/ujson_dumps_float.py')   # requires floating point
             skip_tests.add('extmod/ujson_loads_float.py')   # requires floating point
+            skip_tests.add('basics/exception_chain.py')     # warning is not printed
 
     # Some tests are known to fail on 64-bit machines
     if pyb is None and platform.architecture()[0] == '64bit':