prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  Maybe a bug about module checking
  ### Bug description
  <!-- Use this section to clearly and concisely describe the bug. -->
  If I use conda to install only jupyterhub and python (conda install -c conda-forge python=3.9 jupyterhub), the following message showed as someone try to login:
  
  ```
  Failed to set groups [Errno 1] Operation not permitted
  Traceback (most recent call last):
    File "/home/someone/bin/anaconda3/envs/py39jupyterhub222/bin/jupyterhub-singleuser", line 7, in <module>
      from jupyterhub.singleuser import main
    File "/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/jupyterhub/singleuser/__init__.py", line 5, in <module>
      from .app import main
    File "/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/jupyterhub/singleuser/app.py", line 38, in <module>
      raise _import_error
  TypeError: exceptions must derive from BaseException
  ```
  I think the problem is the lines from 32 to 36 in jupyterhub/singleuser/app.py
  ```
          except ImportError as e:
              continue
              if _import_error is None:
                  _import_error = e
          else:
              break
  ```
  
  I changed that with:
  ```
          except ImportError as e:
              if _import_error is None:
                   _import_error = e
              else:
                  break
              continue
  ```
  then the better message showed:
  ```
  Failed to set groups [Errno 1] Operation not permitted
  Traceback (most recent call last):
    File "/home/someone/bin/anaconda3/envs/py39jupyterhub222/bin/jupyterhub-singleuser", line 7, in <module>
      from jupyterhub.singleuser import main
    File "/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/jupyterhub/singleuser/__init__.py", line 5, in <module>
      from .app import main
    File "/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/jupyterhub/singleuser/app.py", line 38, in <module>
      raise _import_error
    File "/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/jupyterhub/singleuser/app.py", line 30, in <module>
      App = import_item(JUPYTERHUB_SINGLEUSER_APP)
    File "/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/traitlets/utils/importstring.py", line 30, in import_item
      module = __import__(package, fromlist=[obj])
  ModuleNotFoundError: No module named 'jupyter_server'
  ```
  The above message let me know that I have to install jupyter_server.
  This issue can be closed anytime.
  Any suggestion is welcome.
  
  
  </issue>
  <code>
  [start of jupyterhub/singleuser/app.py]
  1 """Make a single-user app based on the environment:
  2 
  3 - $JUPYTERHUB_SINGLEUSER_APP, the base Application class, to be wrapped in JupyterHub authentication.
  4   default: jupyter_server.serverapp.ServerApp
  5 
  6 .. versionchanged:: 2.0
  7 
  8     Default app changed to launch `jupyter labhub`.
  9     Use JUPYTERHUB_SINGLEUSER_APP=notebook.notebookapp.NotebookApp for the legacy 'classic' notebook server.
  10 """
  11 import os
  12 
  13 from traitlets import import_item
  14 
  15 from .mixins import make_singleuser_app
  16 
  17 JUPYTERHUB_SINGLEUSER_APP = os.environ.get("JUPYTERHUB_SINGLEUSER_APP")
  18 
  19 
  20 if JUPYTERHUB_SINGLEUSER_APP:
  21     App = import_item(JUPYTERHUB_SINGLEUSER_APP)
  22 else:
  23     App = None
  24     _import_error = None
  25     for JUPYTERHUB_SINGLEUSER_APP in (
  26         "jupyter_server.serverapp.ServerApp",
  27         "notebook.notebookapp.NotebookApp",
  28     ):
  29         try:
  30             App = import_item(JUPYTERHUB_SINGLEUSER_APP)
  31         except ImportError as e:
  32             continue
  33             if _import_error is None:
  34                 _import_error = e
  35         else:
  36             break
  37     if App is None:
  38         raise _import_error
  39 
  40 
  41 SingleUserNotebookApp = make_singleuser_app(App)
  42 
  43 
  44 def main():
  45     """Launch a jupyterhub single-user server"""
  46     if not os.environ.get("JUPYTERHUB_SINGLEUSER_APP"):
  47         # app not specified, launch jupyter-labhub by default,
  48         # if jupyterlab is recent enough (3.1).
  49         # This is a minimally extended ServerApp that does:
  50         # 1. ensure lab extension is enabled, and
  51         # 2. set default URL to `/lab`
  52         import re
  53 
  54         _version_pat = re.compile(r"(\d+)\.(\d+)")
  55         try:
  56             import jupyterlab
  57             from jupyterlab.labhubapp import SingleUserLabApp
  58 
  59             m = _version_pat.match(jupyterlab.__version__)
  60         except Exception:
  61             m = None
  62 
  63         if m is not None:
  64             version_tuple = tuple(int(v) for v in m.groups())
  65             if version_tuple >= (3, 1):
  66                 return SingleUserLabApp.launch_instance()
  67 
  68     return SingleUserNotebookApp.launch_instance()
  69
  [end of jupyterhub/singleuser/app.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/jupyterhub/singleuser/app.py b/jupyterhub/singleuser/app.py
  --- a/jupyterhub/singleuser/app.py
  +++ b/jupyterhub/singleuser/app.py
  @@ -29,9 +29,9 @@
           try:
               App = import_item(JUPYTERHUB_SINGLEUSER_APP)
           except ImportError as e:
  -            continue
               if _import_error is None:
                   _import_error = e
  +            continue
           else:
               break
       if App is None:
  
verification_info: {"golden_diff": "diff --git a/jupyterhub/singleuser/app.py b/jupyterhub/singleuser/app.py\n--- a/jupyterhub/singleuser/app.py\n+++ b/jupyterhub/singleuser/app.py\n@@ -29,9 +29,9 @@\n         try:\n             App = import_item(JUPYTERHUB_SINGLEUSER_APP)\n         except ImportError as e:\n-            continue\n             if _import_error is None:\n                 _import_error = e\n+            continue\n         else:\n             break\n     if App is None:\n", "issue": "Maybe a bug about module checking\n### Bug description\r\n<!-- Use this section to clearly and concisely describe the bug. -->\r\nIf I use conda to install only jupyterhub and python (conda install -c conda-forge python=3.9 jupyterhub), the following message showed as someone try to login:\r\n\r\n```\r\nFailed to set groups [Errno 1] Operation not permitted\r\nTraceback (most recent call last):\r\n  File \"/home/someone/bin/anaconda3/envs/py39jupyterhub222/bin/jupyterhub-singleuser\", line 7, in <module>\r\n    from jupyterhub.singleuser import main\r\n  File \"/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/jupyterhub/singleuser/__init__.py\", line 5, in <module>\r\n    from .app import main\r\n  File \"/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/jupyterhub/singleuser/app.py\", line 38, in <module>\r\n    raise _import_error\r\nTypeError: exceptions must derive from BaseException\r\n```\r\nI think the problem is the lines from 32 to 36 in jupyterhub/singleuser/app.py\r\n```\r\n        except ImportError as e:\r\n            continue\r\n            if _import_error is None:\r\n                _import_error = e\r\n        else:\r\n            break\r\n```\r\n\r\nI changed that with:\r\n```\r\n        except ImportError as e:\r\n            if _import_error is None:\r\n                 _import_error = e\r\n            else:\r\n                break\r\n            continue\r\n```\r\nthen the better message showed:\r\n```\r\nFailed to set groups [Errno 1] Operation not permitted\r\nTraceback (most recent call last):\r\n  File \"/home/someone/bin/anaconda3/envs/py39jupyterhub222/bin/jupyterhub-singleuser\", line 7, in <module>\r\n    from jupyterhub.singleuser import main\r\n  File \"/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/jupyterhub/singleuser/__init__.py\", line 5, in <module>\r\n    from .app import main\r\n  File \"/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/jupyterhub/singleuser/app.py\", line 38, in <module>\r\n    raise _import_error\r\n  File \"/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/jupyterhub/singleuser/app.py\", line 30, in <module>\r\n    App = import_item(JUPYTERHUB_SINGLEUSER_APP)\r\n  File \"/home/someone/bin/anaconda3/envs/py39jupyterhub222/lib/python3.9/site-packages/traitlets/utils/importstring.py\", line 30, in import_item\r\n    module = __import__(package, fromlist=[obj])\r\nModuleNotFoundError: No module named 'jupyter_server'\r\n```\r\nThe above message let me know that I have to install jupyter_server.\r\nThis issue can be closed anytime.\r\nAny suggestion is welcome.\r\n\n", "before_files": [{"content": "\"\"\"Make a single-user app based on the environment:\n\n- $JUPYTERHUB_SINGLEUSER_APP, the base Application class, to be wrapped in JupyterHub authentication.\n  default: jupyter_server.serverapp.ServerApp\n\n.. versionchanged:: 2.0\n\n    Default app changed to launch `jupyter labhub`.\n    Use JUPYTERHUB_SINGLEUSER_APP=notebook.notebookapp.NotebookApp for the legacy 'classic' notebook server.\n\"\"\"\nimport os\n\nfrom traitlets import import_item\n\nfrom .mixins import make_singleuser_app\n\nJUPYTERHUB_SINGLEUSER_APP = os.environ.get(\"JUPYTERHUB_SINGLEUSER_APP\")\n\n\nif JUPYTERHUB_SINGLEUSER_APP:\n    App = import_item(JUPYTERHUB_SINGLEUSER_APP)\nelse:\n    App = None\n    _import_error = None\n    for JUPYTERHUB_SINGLEUSER_APP in (\n        \"jupyter_server.serverapp.ServerApp\",\n        \"notebook.notebookapp.NotebookApp\",\n    ):\n        try:\n            App = import_item(JUPYTERHUB_SINGLEUSER_APP)\n        except ImportError as e:\n            continue\n            if _import_error is None:\n                _import_error = e\n        else:\n            break\n    if App is None:\n        raise _import_error\n\n\nSingleUserNotebookApp = make_singleuser_app(App)\n\n\ndef main():\n    \"\"\"Launch a jupyterhub single-user server\"\"\"\n    if not os.environ.get(\"JUPYTERHUB_SINGLEUSER_APP\"):\n        # app not specified, launch jupyter-labhub by default,\n        # if jupyterlab is recent enough (3.1).\n        # This is a minimally extended ServerApp that does:\n        # 1. ensure lab extension is enabled, and\n        # 2. set default URL to `/lab`\n        import re\n\n        _version_pat = re.compile(r\"(\\d+)\\.(\\d+)\")\n        try:\n            import jupyterlab\n            from jupyterlab.labhubapp import SingleUserLabApp\n\n            m = _version_pat.match(jupyterlab.__version__)\n        except Exception:\n            m = None\n\n        if m is not None:\n            version_tuple = tuple(int(v) for v in m.groups())\n            if version_tuple >= (3, 1):\n                return SingleUserLabApp.launch_instance()\n\n    return SingleUserNotebookApp.launch_instance()\n", "path": "jupyterhub/singleuser/app.py"}]}