Fix a mypyc compilation error in 3.5 (#5618)

The call to bool() used to disguise the branch wasn't being
semantically analyzed when the version check matched, so work around
that. The actual solution here is to actually handle this case, but
this works for now.

Author: msullivan

mypy/fastparse.py

@@ -80,7 +80,7 @@ def _overload(x: Any) -> Any:
 
 
 # mypyc doesn't like unreachable code, so trick mypy into thinking the branch is reachable
-if sys.version_info < (3, 6) or bool():
+if bool() or sys.version_info < (3, 6):
     overload = _overload  # noqa