slapos.cookbook: Fix publish_failsafe

Do not return installed files in order to avoid endless Uninstall/Install of
the part and instead use the uninstall hook to handle the file when part is
uinstalled.

Also re-install during update if there was a problem with publishing during
install; note that checking for file presence on each update is very fast, so
the speed gain is preserved.

setup.py

@@ -166,6 +166,10 @@ setup(name=name,
           'zero-knowledge.read = slapos.recipe.zero_knowledge:ReadRecipe',
           'zero-knowledge.write = slapos.recipe.zero_knowledge:WriteRecipe'
         ],
+        'zc.buildout.uninstall': [
+          'publish_failsafe = slapos.recipe.publish:RecipeFailsafe.uninstall',
+          'publish.serialised_failsafe = slapos.recipe.publish:SerialisedFailsafe.uninstall',
+        ]
       },
       extras_require=extras_require,
       test_suite='slapos.test',

slapos/recipe/publish.py

@@ -71,9 +71,9 @@ class Serialised(Recipe):
 class Failsafe(object):
   def _setConnectionDict(self, publish_dict, slave_reference):
     error_status_file = self.options.get('-error-status-file')
-    if error_status_file:
-      self.return_list = [error_status_file]
-    else:
+    # Note: We can't put -error-status-file in return list as by default it is
+    #       not present, and buildout wants the section to have it, so it
+    #       Uninstalls/Installs the part instead of just Updating it
     self.return_list = []
     try:
       super(Failsafe, self)._setConnectionDict(publish_dict, slave_reference)
@@ -86,6 +86,19 @@ class Failsafe(object):
         if os.path.exists(error_status_file):
           os.unlink(error_status_file)
 
+  def update(self):
+    error_status_file = self.options.get('-error-status-file')
+    if error_status_file is not None:
+      if os.path.exists(error_status_file):
+        # last run failed, so need to reinstall
+        self.install()
+
+  def uninstall(name, options):
+    error_status_file = options.get('-error-status-file')
+    if error_status_file is not None:
+      if os.path.exists(error_status_file):
+        os.unlink(error_status_file)
+
 
 class RecipeFailsafe(Failsafe, Recipe):
   pass