fixup! [SlapOS Core] Improve configure-local command and add test for this command

To copy those files we should check first if exists because after generate the
egg those files does not exist anymore and it blocks to install the package

setup.py

@@ -14,8 +14,10 @@ for f in sorted(glob.glob(os.path.join('slapos', 'README.*.txt'))):
 slapos_folder_path = os.path.dirname(__file__)
 for template_name in ('slapos-client.cfg.example',
     'slapos-proxy.cfg.example', 'slapos.cfg.example'):
-  copyfile(os.path.join(slapos_folder_path, template_name),
-    os.path.join(slapos_folder_path, 'slapos', template_name))
+  template_path = os.path.join(slapos_folder_path, template_name)
+  if os.path.exists(template_path):
+    copyfile(template_path,
+      os.path.join(slapos_folder_path, 'slapos', template_name))
 
 additional_install_requires = []
 # Even if argparse is available in python2.7, some python2.7 installations