issue #590: include nasty workaround for sys.modules junk

Author: dw

ansible_mitogen/runner.py

@@ -760,7 +760,12 @@ def _setup_imports(self):
         for fullname, _, _ in self.module_map['custom']:
             mitogen.core.import_module(fullname)
         for fullname in self.module_map['builtin']:
-            mitogen.core.import_module(fullname)
+            try:
+                mitogen.core.import_module(fullname)
+            except ImportError:
+                # TODO: this is a huge hack to work around issue #590.
+                if fullname != 'ansible.module_utils.distro._distro':
+                    raise
 
     def _setup_excepthook(self):
         """