Make PyMySQL work in the package generated by py2exe

Setting the 'optimize' level to 2 was causing pymysql imports to
fail. This sets the 'optimize' level to 1 solving the issue.

This is equivalent to the change in d713b36 for py2app.

setup.py

@@ -92,7 +92,7 @@ def clean_version(v):
       # to bundle_files = 3 and Inno Setup
       options = {'py2exe': {'bundle_files': 3,
                             'compressed': 2,
-                            'optimize': 2,
+                            'optimize': 1,
                             'packages': packages,
                             'includes': includes,
                             'excludes': excludes,