prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  Cannot edit or delete challenge pages with slug `evaluation`
  
  
  </issue>
  <code>
  [start of app/grandchallenge/pages/forms.py]
  1 from django import forms
  2 from django.db.models import BLANK_CHOICE_DASH
  3 from django_summernote.widgets import SummernoteInplaceWidget
  4 
  5 from grandchallenge.core.forms import SaveFormInitMixin
  6 from grandchallenge.pages.models import Page
  7 
  8 
  9 class PageCreateForm(SaveFormInitMixin, forms.ModelForm):
  10     def __init__(self, *args, challenge, **kwargs):
  11         self.challenge = challenge
  12         super().__init__(*args, **kwargs)
  13 
  14     class Meta:
  15         model = Page
  16         fields = (
  17             "display_title",
  18             "permission_level",
  19             "hidden",
  20             "html",
  21         )
  22         widgets = {"html": SummernoteInplaceWidget()}
  23         help_texts = {
  24             "html": (
  25                 "The content of your page. <b>Please note</b>: your html will "
  26                 "be filtered after it has been saved to remove any non-HTML5 "
  27                 "compliant markup and scripts. The filtering is not reflected "
  28                 "in the live view so please <b>check the rendering of your "
  29                 "page after you click save</b>. If you're going to paste from "
  30                 "another source such as MS Word, please <b>paste without "
  31                 "formatting</b> using <b>CTRL+SHIFT+V</b> on Windows or "
  32                 "<b>⇧+⌥+⌘+V</b> on OS X."
  33             )
  34         }
  35 
  36 
  37 class PageUpdateForm(PageCreateForm):
  38     """Like the page update form but you can also move the page."""
  39 
  40     move = forms.CharField(widget=forms.Select)
  41     move.required = False
  42     move.widget.choices = (
  43         (BLANK_CHOICE_DASH[0]),
  44         (Page.FIRST, "First"),
  45         (Page.UP, "Up"),
  46         (Page.DOWN, "Down"),
  47         (Page.LAST, "Last"),
  48     )
  49
  [end of app/grandchallenge/pages/forms.py]
  </code>
  
  I need you to solve this issue by generating a single patch file that I can apply directly to this repository using git apply. Please respond with a single patch file in the following format.
  <patch>
  diff --git a/file.py b/file.py
  --- a/file.py
  +++ b/file.py
  @@ -1,27 +1,35 @@
   def euclidean(a, b):
  -    while b:
  -        a, b = b, a % b
  -    return a
  +    if b == 0:
  +        return a
  +    return euclidean(b, a % b)
   
   
   def bresenham(x0, y0, x1, y1):
       points = []
       dx = abs(x1 - x0)
       dy = abs(y1 - y0)
  -    sx = 1 if x0 < x1 else -1
  -    sy = 1 if y0 < y1 else -1
  -    err = dx - dy
  +    x, y = x0, y0
  +    sx = -1 if x0 > x1 else 1
  +    sy = -1 if y0 > y1 else 1
   
  -    while True:
  -        points.append((x0, y0))
  -        if x0 == x1 and y0 == y1:
  -            break
  -        e2 = 2 * err
  -        if e2 > -dy:
  -            err -= dy
  -            x0 += sx
  -        if e2 < dx:
  -            err += dx
  -            y0 += sy
  +    if dx > dy:
  +        err = dx / 2.0
  +        while x != x1:
  +            points.append((x, y))
  +            err -= dy
  +            if err < 0:
  +                y += sy
  +                err += dx
  +            x += sx
  +    else:
  +        err = dy / 2.0
  +        while y != y1:
  +            points.append((x, y))
  +            err -= dx
  +            if err < 0:
  +                x += sx
  +                err += dy
  +            y += sy
  +
  +    points.append((x, y))
       return points
  
  </patch>
golden_diff: diff --git a/app/grandchallenge/pages/forms.py b/app/grandchallenge/pages/forms.py
  --- a/app/grandchallenge/pages/forms.py
  +++ b/app/grandchallenge/pages/forms.py
  @@ -1,4 +1,5 @@
   from django import forms
  +from django.core.exceptions import ValidationError
   from django.db.models import BLANK_CHOICE_DASH
   from django_summernote.widgets import SummernoteInplaceWidget
   
  @@ -33,6 +34,17 @@
               )
           }
   
  +    def clean_display_title(self):
  +        display_title = self.cleaned_data["display_title"]
  +
  +        if display_title.lower() in {"evaluation"}:
  +            # evaluation results in a URL clash, especially with the update page.
  +            raise ValidationError(
  +                "Title not allowed, please select an alternative"
  +            )
  +
  +        return display_title
  +
   
   class PageUpdateForm(PageCreateForm):
       """Like the page update form but you can also move the page."""
  
verification_info: {"golden_diff": "diff --git a/app/grandchallenge/pages/forms.py b/app/grandchallenge/pages/forms.py\n--- a/app/grandchallenge/pages/forms.py\n+++ b/app/grandchallenge/pages/forms.py\n@@ -1,4 +1,5 @@\n from django import forms\n+from django.core.exceptions import ValidationError\n from django.db.models import BLANK_CHOICE_DASH\n from django_summernote.widgets import SummernoteInplaceWidget\n \n@@ -33,6 +34,17 @@\n             )\n         }\n \n+    def clean_display_title(self):\n+        display_title = self.cleaned_data[\"display_title\"]\n+\n+        if display_title.lower() in {\"evaluation\"}:\n+            # evaluation results in a URL clash, especially with the update page.\n+            raise ValidationError(\n+                \"Title not allowed, please select an alternative\"\n+            )\n+\n+        return display_title\n+\n \n class PageUpdateForm(PageCreateForm):\n     \"\"\"Like the page update form but you can also move the page.\"\"\"\n", "issue": "Cannot edit or delete challenge pages with slug `evaluation`\n\n", "before_files": [{"content": "from django import forms\nfrom django.db.models import BLANK_CHOICE_DASH\nfrom django_summernote.widgets import SummernoteInplaceWidget\n\nfrom grandchallenge.core.forms import SaveFormInitMixin\nfrom grandchallenge.pages.models import Page\n\n\nclass PageCreateForm(SaveFormInitMixin, forms.ModelForm):\n    def __init__(self, *args, challenge, **kwargs):\n        self.challenge = challenge\n        super().__init__(*args, **kwargs)\n\n    class Meta:\n        model = Page\n        fields = (\n            \"display_title\",\n            \"permission_level\",\n            \"hidden\",\n            \"html\",\n        )\n        widgets = {\"html\": SummernoteInplaceWidget()}\n        help_texts = {\n            \"html\": (\n                \"The content of your page. <b>Please note</b>: your html will \"\n                \"be filtered after it has been saved to remove any non-HTML5 \"\n                \"compliant markup and scripts. The filtering is not reflected \"\n                \"in the live view so please <b>check the rendering of your \"\n                \"page after you click save</b>. If you're going to paste from \"\n                \"another source such as MS Word, please <b>paste without \"\n                \"formatting</b> using <b>CTRL+SHIFT+V</b> on Windows or \"\n                \"<b>\u21e7+\u2325+\u2318+V</b> on OS X.\"\n            )\n        }\n\n\nclass PageUpdateForm(PageCreateForm):\n    \"\"\"Like the page update form but you can also move the page.\"\"\"\n\n    move = forms.CharField(widget=forms.Select)\n    move.required = False\n    move.widget.choices = (\n        (BLANK_CHOICE_DASH[0]),\n        (Page.FIRST, \"First\"),\n        (Page.UP, \"Up\"),\n        (Page.DOWN, \"Down\"),\n        (Page.LAST, \"Last\"),\n    )\n", "path": "app/grandchallenge/pages/forms.py"}]}