[mypyc] Report warnings when compilation is successful

mypyc/emitmodule.py

diff --git a/mypyc/emitmodule.py b/mypyc/emitmodule.py
index 9a52f9d..023e8bf 100644
--- a/mypyc/emitmodule.py
+++ b/mypyc/emitmodule.py
@@ -112,6 +112,7 @@
     modules = genops.build_ir(file_nodes, result.graph, result.types,
                               mapper,
                               compiler_options, errors)
+    errors.flush_errors()
     if errors.num_errors > 0:
         return modules, []
     # Insert uninit checks.