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()

```

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

{"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"}]}