prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  Catalog exists property throws "CandidateNotFound" Exception
  When we call <catalog_obj>.exists , it throws  "CandidateNotFound" Exception, where as in our test cases  we expect a Boolean value "False"
  >> https://github.com/ManageIQ/integration_tests/blob/master/cfme/services/catalogs/catalog.py#L119 
  
  Steps to Reproduce: <catalog_obj>.exists
  Actual Result:  Trace-back of   "CandidateNotFound" Exception
  Expected Result: False 
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `cfme/services/catalogs/catalog.py`
  Content:
  ```
  1 import attr
  2 
  3 from widgetastic.utils import Parameter
  4 from widgetastic.widget import Text
  5 from widgetastic_manageiq import MultiBoxSelect
  6 from widgetastic_patternfly import Button, Input
  7 from navmazing import NavigateToAttribute, NavigateToSibling
  8 
  9 from cfme.common import Taggable
  10 from cfme.modeling.base import BaseCollection, BaseEntity
  11 from cfme.utils.appliance.implementations.ui import navigator, CFMENavigateStep, navigate_to
  12 from cfme.utils.pretty import Pretty
  13 from cfme.utils.update import Updateable
  14 from cfme.utils.wait import wait_for
  15 
  16 from . import ServicesCatalogView
  17 
  18 
  19 class CatalogsMultiBoxSelect(MultiBoxSelect):
  20     move_into_button = Button(title=Parameter("@move_into"))
  21     move_from_button = Button(title=Parameter("@move_from"))
  22 
  23 
  24 class CatalogForm(ServicesCatalogView):
  25     title = Text('#explorer_title_text')
  26 
  27     name = Input(name='name')
  28     description = Input(name="description")
  29     assign_catalog_items = CatalogsMultiBoxSelect(
  30         move_into="Move Selected buttons right",
  31         move_from="Move Selected buttons left",
  32         available_items="available_fields",
  33         chosen_items="selected_fields"
  34     )
  35 
  36     save_button = Button('Save')
  37     cancel_button = Button('Cancel')
  38 
  39 
  40 class CatalogsView(ServicesCatalogView):
  41     title = Text("#explorer_title_text")
  42 
  43     @property
  44     def is_displayed(self):
  45         return (
  46             self.in_explorer and
  47             self.catalogs.is_opened and
  48             self.catalogs.tree.currently_selected == ["All Catalogs"])
  49 
  50 
  51 class DetailsCatalogView(ServicesCatalogView):
  52     title = Text("#explorer_title_text")
  53 
  54     @property
  55     def is_displayed(self):
  56         return (
  57             self.in_explorer and self.catalogs.is_opened and
  58             self.title.text == 'Catalog "{}"'.format(self.context["object"].name)
  59         )
  60 
  61 
  62 class AddCatalogView(CatalogForm):
  63 
  64     add_button = Button("Add")
  65 
  66     @property
  67     def is_displayed(self):
  68         return (
  69             self.in_explorer and self.catalogs.is_opened and
  70             self.title.text == 'Adding a new Catalog'
  71         )
  72 
  73 
  74 class EditCatalogView(CatalogForm):
  75 
  76     save_button = Button('Save')
  77     reset_button = Button('Reset')
  78 
  79     @property
  80     def is_displayed(self):
  81         return (
  82             self.in_explorer and self.catalogs.is_opened and
  83             self.title.text == 'Editing Catalog "{}"'.format(self.context["object"].name)
  84         )
  85 
  86 
  87 @attr.s
  88 class Catalog(BaseEntity, Updateable, Pretty, Taggable):
  89 
  90     name = attr.ib()
  91     description = attr.ib()
  92     items = attr.ib(default=None)
  93 
  94     def update(self, updates):
  95         view = navigate_to(self, 'Edit')
  96         changed = view.fill(updates)
  97         if changed:
  98             view.save_button.click()
  99         else:
  100             view.cancel_button.click()
  101         view = self.create_view(DetailsCatalogView, override=updates, wait='10s')
  102         view.flash.assert_no_error()
  103         if changed:
  104             view.flash.assert_message(
  105                 'Catalog "{}" was saved'.format(updates.get('name', self.name)))
  106         else:
  107             view.flash.assert_message(
  108                 'Edit of Catalog "{}" was cancelled by the user'.format(self.name))
  109 
  110     def delete(self):
  111         view = navigate_to(self, "Details")
  112         view.configuration.item_select('Remove Catalog', handle_alert=True)
  113         view = self.create_view(CatalogsView, wait='10s')
  114         view.flash.assert_no_error()
  115         view.flash.assert_success_message(
  116             'Catalog "{}": Delete successful'.format(self.description or self.name))
  117 
  118     @property
  119     def exists(self):
  120         try:
  121             navigate_to(self, 'Details')
  122             return True
  123         except NameError:
  124             return False
  125 
  126 
  127 @attr.s
  128 class CatalogCollection(BaseCollection):
  129     """A collection for the :py:class:`cfme.services.catalogs.catalog.Catalog`"""
  130     ENTITY = Catalog
  131 
  132     def create(self, name, description, items=None):
  133         """Create a catalog.
  134 
  135         Args:
  136             name: The name of the catalog
  137             description: The description of the catalog
  138             items: Items in the catalog
  139         """
  140         view = navigate_to(self, 'Add')
  141         view.fill({
  142             'name': name,
  143             'description': description,
  144             'assign_catalog_items': items
  145         })
  146         view.add_button.click()
  147         catalog = self.instantiate(name=name, description=description, items=items)
  148         view = self.create_view(CatalogsView)
  149         assert view.is_displayed
  150         view.flash.assert_no_error()
  151         return catalog
  152 
  153 
  154 @navigator.register(CatalogCollection)
  155 class All(CFMENavigateStep):
  156     VIEW = CatalogsView
  157     prerequisite = NavigateToAttribute('appliance.server', 'LoggedIn')
  158 
  159     def step(self):
  160         self.prerequisite_view.navigation.select('Services', 'Catalogs')
  161         self.view.catalogs.tree.click_path("All Catalogs")
  162 
  163 
  164 @navigator.register(CatalogCollection)
  165 class Add(CFMENavigateStep):
  166     VIEW = AddCatalogView
  167     prerequisite = NavigateToSibling('All')
  168 
  169     def step(self):
  170         self.prerequisite_view.configuration.item_select('Add a New Catalog')
  171 
  172 
  173 @navigator.register(Catalog)
  174 class Details(CFMENavigateStep):
  175     VIEW = DetailsCatalogView
  176     prerequisite = NavigateToAttribute('parent', 'All')
  177 
  178     def step(self):
  179         self.prerequisite_view.catalogs.tree.click_path("All Catalogs", self.obj.name)
  180 
  181 
  182 @navigator.register(Catalog)
  183 class Edit(CFMENavigateStep):
  184     VIEW = EditCatalogView
  185     prerequisite = NavigateToSibling('Details')
  186 
  187     def step(self):
  188         self.prerequisite_view.configuration.item_select('Edit this Item')
  189
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/cfme/services/catalogs/catalog.py b/cfme/services/catalogs/catalog.py
  --- a/cfme/services/catalogs/catalog.py
  +++ b/cfme/services/catalogs/catalog.py
  @@ -3,7 +3,7 @@
   from widgetastic.utils import Parameter
   from widgetastic.widget import Text
   from widgetastic_manageiq import MultiBoxSelect
  -from widgetastic_patternfly import Button, Input
  +from widgetastic_patternfly import Button, CandidateNotFound, Input
   from navmazing import NavigateToAttribute, NavigateToSibling
   
   from cfme.common import Taggable
  @@ -120,7 +120,7 @@
           try:
               navigate_to(self, 'Details')
               return True
  -        except NameError:
  +        except (NameError, CandidateNotFound):
               return False
  
verification_info: {"golden_diff": "diff --git a/cfme/services/catalogs/catalog.py b/cfme/services/catalogs/catalog.py\n--- a/cfme/services/catalogs/catalog.py\n+++ b/cfme/services/catalogs/catalog.py\n@@ -3,7 +3,7 @@\n from widgetastic.utils import Parameter\n from widgetastic.widget import Text\n from widgetastic_manageiq import MultiBoxSelect\n-from widgetastic_patternfly import Button, Input\n+from widgetastic_patternfly import Button, CandidateNotFound, Input\n from navmazing import NavigateToAttribute, NavigateToSibling\n \n from cfme.common import Taggable\n@@ -120,7 +120,7 @@\n         try:\n             navigate_to(self, 'Details')\n             return True\n-        except NameError:\n+        except (NameError, CandidateNotFound):\n             return False\n", "issue": "Catalog exists property throws \"CandidateNotFound\" Exception\nWhen we call <catalog_obj>.exists , it throws  \"CandidateNotFound\" Exception, where as in our test cases  we expect a Boolean value \"False\"\r\n>> https://github.com/ManageIQ/integration_tests/blob/master/cfme/services/catalogs/catalog.py#L119 \r\n\r\nSteps to Reproduce: <catalog_obj>.exists\r\nActual Result:  Trace-back of   \"CandidateNotFound\" Exception\r\nExpected Result: False \n", "before_files": [{"content": "import attr\n\nfrom widgetastic.utils import Parameter\nfrom widgetastic.widget import Text\nfrom widgetastic_manageiq import MultiBoxSelect\nfrom widgetastic_patternfly import Button, Input\nfrom navmazing import NavigateToAttribute, NavigateToSibling\n\nfrom cfme.common import Taggable\nfrom cfme.modeling.base import BaseCollection, BaseEntity\nfrom cfme.utils.appliance.implementations.ui import navigator, CFMENavigateStep, navigate_to\nfrom cfme.utils.pretty import Pretty\nfrom cfme.utils.update import Updateable\nfrom cfme.utils.wait import wait_for\n\nfrom . import ServicesCatalogView\n\n\nclass CatalogsMultiBoxSelect(MultiBoxSelect):\n    move_into_button = Button(title=Parameter(\"@move_into\"))\n    move_from_button = Button(title=Parameter(\"@move_from\"))\n\n\nclass CatalogForm(ServicesCatalogView):\n    title = Text('#explorer_title_text')\n\n    name = Input(name='name')\n    description = Input(name=\"description\")\n    assign_catalog_items = CatalogsMultiBoxSelect(\n        move_into=\"Move Selected buttons right\",\n        move_from=\"Move Selected buttons left\",\n        available_items=\"available_fields\",\n        chosen_items=\"selected_fields\"\n    )\n\n    save_button = Button('Save')\n    cancel_button = Button('Cancel')\n\n\nclass CatalogsView(ServicesCatalogView):\n    title = Text(\"#explorer_title_text\")\n\n    @property\n    def is_displayed(self):\n        return (\n            self.in_explorer and\n            self.catalogs.is_opened and\n            self.catalogs.tree.currently_selected == [\"All Catalogs\"])\n\n\nclass DetailsCatalogView(ServicesCatalogView):\n    title = Text(\"#explorer_title_text\")\n\n    @property\n    def is_displayed(self):\n        return (\n            self.in_explorer and self.catalogs.is_opened and\n            self.title.text == 'Catalog \"{}\"'.format(self.context[\"object\"].name)\n        )\n\n\nclass AddCatalogView(CatalogForm):\n\n    add_button = Button(\"Add\")\n\n    @property\n    def is_displayed(self):\n        return (\n            self.in_explorer and self.catalogs.is_opened and\n            self.title.text == 'Adding a new Catalog'\n        )\n\n\nclass EditCatalogView(CatalogForm):\n\n    save_button = Button('Save')\n    reset_button = Button('Reset')\n\n    @property\n    def is_displayed(self):\n        return (\n            self.in_explorer and self.catalogs.is_opened and\n            self.title.text == 'Editing Catalog \"{}\"'.format(self.context[\"object\"].name)\n        )\n\n\n@attr.s\nclass Catalog(BaseEntity, Updateable, Pretty, Taggable):\n\n    name = attr.ib()\n    description = attr.ib()\n    items = attr.ib(default=None)\n\n    def update(self, updates):\n        view = navigate_to(self, 'Edit')\n        changed = view.fill(updates)\n        if changed:\n            view.save_button.click()\n        else:\n            view.cancel_button.click()\n        view = self.create_view(DetailsCatalogView, override=updates, wait='10s')\n        view.flash.assert_no_error()\n        if changed:\n            view.flash.assert_message(\n                'Catalog \"{}\" was saved'.format(updates.get('name', self.name)))\n        else:\n            view.flash.assert_message(\n                'Edit of Catalog \"{}\" was cancelled by the user'.format(self.name))\n\n    def delete(self):\n        view = navigate_to(self, \"Details\")\n        view.configuration.item_select('Remove Catalog', handle_alert=True)\n        view = self.create_view(CatalogsView, wait='10s')\n        view.flash.assert_no_error()\n        view.flash.assert_success_message(\n            'Catalog \"{}\": Delete successful'.format(self.description or self.name))\n\n    @property\n    def exists(self):\n        try:\n            navigate_to(self, 'Details')\n            return True\n        except NameError:\n            return False\n\n\n@attr.s\nclass CatalogCollection(BaseCollection):\n    \"\"\"A collection for the :py:class:`cfme.services.catalogs.catalog.Catalog`\"\"\"\n    ENTITY = Catalog\n\n    def create(self, name, description, items=None):\n        \"\"\"Create a catalog.\n\n        Args:\n            name: The name of the catalog\n            description: The description of the catalog\n            items: Items in the catalog\n        \"\"\"\n        view = navigate_to(self, 'Add')\n        view.fill({\n            'name': name,\n            'description': description,\n            'assign_catalog_items': items\n        })\n        view.add_button.click()\n        catalog = self.instantiate(name=name, description=description, items=items)\n        view = self.create_view(CatalogsView)\n        assert view.is_displayed\n        view.flash.assert_no_error()\n        return catalog\n\n\n@navigator.register(CatalogCollection)\nclass All(CFMENavigateStep):\n    VIEW = CatalogsView\n    prerequisite = NavigateToAttribute('appliance.server', 'LoggedIn')\n\n    def step(self):\n        self.prerequisite_view.navigation.select('Services', 'Catalogs')\n        self.view.catalogs.tree.click_path(\"All Catalogs\")\n\n\n@navigator.register(CatalogCollection)\nclass Add(CFMENavigateStep):\n    VIEW = AddCatalogView\n    prerequisite = NavigateToSibling('All')\n\n    def step(self):\n        self.prerequisite_view.configuration.item_select('Add a New Catalog')\n\n\n@navigator.register(Catalog)\nclass Details(CFMENavigateStep):\n    VIEW = DetailsCatalogView\n    prerequisite = NavigateToAttribute('parent', 'All')\n\n    def step(self):\n        self.prerequisite_view.catalogs.tree.click_path(\"All Catalogs\", self.obj.name)\n\n\n@navigator.register(Catalog)\nclass Edit(CFMENavigateStep):\n    VIEW = EditCatalogView\n    prerequisite = NavigateToSibling('Details')\n\n    def step(self):\n        self.prerequisite_view.configuration.item_select('Edit this Item')\n", "path": "cfme/services/catalogs/catalog.py"}], "after_files": [{"content": "import attr\n\nfrom widgetastic.utils import Parameter\nfrom widgetastic.widget import Text\nfrom widgetastic_manageiq import MultiBoxSelect\nfrom widgetastic_patternfly import Button, CandidateNotFound, Input\nfrom navmazing import NavigateToAttribute, NavigateToSibling\n\nfrom cfme.common import Taggable\nfrom cfme.modeling.base import BaseCollection, BaseEntity\nfrom cfme.utils.appliance.implementations.ui import navigator, CFMENavigateStep, navigate_to\nfrom cfme.utils.pretty import Pretty\nfrom cfme.utils.update import Updateable\nfrom cfme.utils.wait import wait_for\n\nfrom . import ServicesCatalogView\n\n\nclass CatalogsMultiBoxSelect(MultiBoxSelect):\n    move_into_button = Button(title=Parameter(\"@move_into\"))\n    move_from_button = Button(title=Parameter(\"@move_from\"))\n\n\nclass CatalogForm(ServicesCatalogView):\n    title = Text('#explorer_title_text')\n\n    name = Input(name='name')\n    description = Input(name=\"description\")\n    assign_catalog_items = CatalogsMultiBoxSelect(\n        move_into=\"Move Selected buttons right\",\n        move_from=\"Move Selected buttons left\",\n        available_items=\"available_fields\",\n        chosen_items=\"selected_fields\"\n    )\n\n    save_button = Button('Save')\n    cancel_button = Button('Cancel')\n\n\nclass CatalogsView(ServicesCatalogView):\n    title = Text(\"#explorer_title_text\")\n\n    @property\n    def is_displayed(self):\n        return (\n            self.in_explorer and\n            self.catalogs.is_opened and\n            self.catalogs.tree.currently_selected == [\"All Catalogs\"])\n\n\nclass DetailsCatalogView(ServicesCatalogView):\n    title = Text(\"#explorer_title_text\")\n\n    @property\n    def is_displayed(self):\n        return (\n            self.in_explorer and self.catalogs.is_opened and\n            self.title.text == 'Catalog \"{}\"'.format(self.context[\"object\"].name)\n        )\n\n\nclass AddCatalogView(CatalogForm):\n\n    add_button = Button(\"Add\")\n\n    @property\n    def is_displayed(self):\n        return (\n            self.in_explorer and self.catalogs.is_opened and\n            self.title.text == 'Adding a new Catalog'\n        )\n\n\nclass EditCatalogView(CatalogForm):\n\n    save_button = Button('Save')\n    reset_button = Button('Reset')\n\n    @property\n    def is_displayed(self):\n        return (\n            self.in_explorer and self.catalogs.is_opened and\n            self.title.text == 'Editing Catalog \"{}\"'.format(self.context[\"object\"].name)\n        )\n\n\n@attr.s\nclass Catalog(BaseEntity, Updateable, Pretty, Taggable):\n\n    name = attr.ib()\n    description = attr.ib()\n    items = attr.ib(default=None)\n\n    def update(self, updates):\n        view = navigate_to(self, 'Edit')\n        changed = view.fill(updates)\n        if changed:\n            view.save_button.click()\n        else:\n            view.cancel_button.click()\n        view = self.create_view(DetailsCatalogView, override=updates, wait='10s')\n        view.flash.assert_no_error()\n        if changed:\n            view.flash.assert_message(\n                'Catalog \"{}\" was saved'.format(updates.get('name', self.name)))\n        else:\n            view.flash.assert_message(\n                'Edit of Catalog \"{}\" was cancelled by the user'.format(self.name))\n\n    def delete(self):\n        view = navigate_to(self, \"Details\")\n        view.configuration.item_select('Remove Catalog', handle_alert=True)\n        view = self.create_view(CatalogsView, wait='10s')\n        view.flash.assert_no_error()\n        view.flash.assert_success_message(\n            'Catalog \"{}\": Delete successful'.format(self.description or self.name))\n\n    @property\n    def exists(self):\n        try:\n            navigate_to(self, 'Details')\n            return True\n        except (NameError, CandidateNotFound):\n            return False\n\n\n@attr.s\nclass CatalogCollection(BaseCollection):\n    \"\"\"A collection for the :py:class:`cfme.services.catalogs.catalog.Catalog`\"\"\"\n    ENTITY = Catalog\n\n    def create(self, name, description, items=None):\n        \"\"\"Create a catalog.\n\n        Args:\n            name: The name of the catalog\n            description: The description of the catalog\n            items: Items in the catalog\n        \"\"\"\n        view = navigate_to(self, 'Add')\n        view.fill({\n            'name': name,\n            'description': description,\n            'assign_catalog_items': items\n        })\n        view.add_button.click()\n        catalog = self.instantiate(name=name, description=description, items=items)\n        view = self.create_view(CatalogsView)\n        assert view.is_displayed\n        view.flash.assert_no_error()\n        return catalog\n\n\n@navigator.register(CatalogCollection)\nclass All(CFMENavigateStep):\n    VIEW = CatalogsView\n    prerequisite = NavigateToAttribute('appliance.server', 'LoggedIn')\n\n    def step(self):\n        self.prerequisite_view.navigation.select('Services', 'Catalogs')\n        self.view.catalogs.tree.click_path(\"All Catalogs\")\n\n\n@navigator.register(CatalogCollection)\nclass Add(CFMENavigateStep):\n    VIEW = AddCatalogView\n    prerequisite = NavigateToSibling('All')\n\n    def step(self):\n        self.prerequisite_view.configuration.item_select('Add a New Catalog')\n\n\n@navigator.register(Catalog)\nclass Details(CFMENavigateStep):\n    VIEW = DetailsCatalogView\n    prerequisite = NavigateToAttribute('parent', 'All')\n\n    def step(self):\n        self.prerequisite_view.catalogs.tree.click_path(\"All Catalogs\", self.obj.name)\n\n\n@navigator.register(Catalog)\nclass Edit(CFMENavigateStep):\n    VIEW = EditCatalogView\n    prerequisite = NavigateToSibling('Details')\n\n    def step(self):\n        self.prerequisite_view.configuration.item_select('Edit this Item')\n", "path": "cfme/services/catalogs/catalog.py"}]}