prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  Can't start inventree server
  It seems that error at `https://api.exchangerate.host/latest` blocks server startup.
  
  ```
  # curl https://api.exchangerate.host/latest
  <html>
  <head><title>521 Origin Down</title></head>
  <body bgcolor="white">
  <center><h1>521 Origin Down</h1></center>
  <hr><center>cloudflare-nginx</center>
  </body>
  </html>
  ```
  
  <details>
  
  ```
  # inv server
  InvenTree Database Configuration
  ================================
  ENGINE: django.db.backends.mysql
  NAME: inventree
  HOST: localhost
  Base currency changed from USD to RUB
  Updating exchange rates from https://api.exchangerate.host/latest
  Using base currency 'RUB'
  InvenTree Database Configuration
  ================================
  ENGINE: django.db.backends.mysql
  NAME: inventree
  HOST: localhost
  Base currency changed from USD to RUB
  Updating exchange rates from https://api.exchangerate.host/latest
  Using base currency 'RUB'
  Watching for file changes with StatReloader
  Watching for file changes with StatReloader
  Exception in thread django-main-thread:
  Traceback (most recent call last):
    File "/usr/lib64/python3.6/threading.py", line 916, in _bootstrap_inner
      self.run()
    File "/usr/lib64/python3.6/threading.py", line 864, in run
      self._target(*self._args, **self._kwargs)
    File "/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/utils/autoreload.py", line 64, in wrapper
      fn(*args, **kwargs)
    File "/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/core/management/commands/runserver.py", line 110, in inner_run
      autoreload.raise_last_exception()
    File "/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/utils/autoreload.py", line 87, in raise_last_exception
      raise _exception[1]
    File "/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/core/management/__init__.py", line 375, in execute
      autoreload.check_errors(django.setup)()
    File "/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/utils/autoreload.py", line 64, in wrapper
      fn(*args, **kwargs)
    File "/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/__init__.py", line 24, in setup
      apps.populate(settings.INSTALLED_APPS)
    File "/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/apps/registry.py", line 122, in populate
      app_config.ready()
    File "/var/projects/inventree/inventree/InvenTree/InvenTree/apps.py", line 24, in ready
      self.update_exchange_rates()
    File "/var/projects/inventree/inventree/InvenTree/InvenTree/apps.py", line 105, in update_exchange_rates
      update_exchange_rates()
    File "/var/projects/inventree/inventree/InvenTree/InvenTree/tasks.py", line 199, in update_exchange_rates
      backend.update_rates(base_currency=base)
    File "/var/projects/inventree/inventree/InvenTree/InvenTree/exchange.py", line 29, in update_rates
      super().update_rates(base=base_currency, symbols=symbols)
    File "/usr/lib64/python3.6/contextlib.py", line 52, in inner
      return func(*args, **kwds)
    File "/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/djmoney/contrib/exchange/backends/base.py", line 68, in update_rates
      for currency, value in self.get_rates(**params).items()
    File "/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/djmoney/contrib/exchange/backends/base.py", line 80, in get_rates
      response = self.get_response(**params)
    File "/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/djmoney/contrib/exchange/backends/base.py", line 48, in get_response
      response = urlopen(url, cafile=certifi.where())
    File "/usr/lib64/python3.6/urllib/request.py", line 223, in urlopen
      return opener.open(url, data, timeout)
    File "/usr/lib64/python3.6/urllib/request.py", line 532, in open
      response = meth(req, response)
    File "/usr/lib64/python3.6/urllib/request.py", line 642, in http_response
      'http', request, response, code, msg, hdrs)
    File "/usr/lib64/python3.6/urllib/request.py", line 570, in error
      return self._call_chain(*args)
    File "/usr/lib64/python3.6/urllib/request.py", line 504, in _call_chain
      result = func(*args)
    File "/usr/lib64/python3.6/urllib/request.py", line 650, in http_error_default
      raise HTTPError(req.full_url, code, msg, hdrs, fp)
  urllib.error.HTTPError: HTTP Error 521: Origin Down
  ```
  
  </details>
  
  </issue>
  <code>
  [start of InvenTree/InvenTree/exchange.py]
  1 from common.settings import currency_code_default, currency_codes
  2 
  3 from djmoney.contrib.exchange.backends.base import SimpleExchangeBackend
  4 
  5 
  6 class InvenTreeExchange(SimpleExchangeBackend):
  7     """
  8     Backend for automatically updating currency exchange rates.
  9 
  10     Uses the exchangerate.host service API
  11     """
  12 
  13     name = "InvenTreeExchange"
  14 
  15     def __init__(self):
  16         self.url = "https://api.exchangerate.host/latest"
  17 
  18         super().__init__()
  19 
  20     def get_params(self):
  21         # No API key is required
  22         return {
  23         }
  24 
  25     def update_rates(self, base_currency=currency_code_default()):
  26 
  27         symbols = ','.join(currency_codes())
  28 
  29         super().update_rates(base=base_currency, symbols=symbols)
  30
  [end of InvenTree/InvenTree/exchange.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/InvenTree/InvenTree/exchange.py b/InvenTree/InvenTree/exchange.py
  --- a/InvenTree/InvenTree/exchange.py
  +++ b/InvenTree/InvenTree/exchange.py
  @@ -1,4 +1,5 @@
   from common.settings import currency_code_default, currency_codes
  +from urllib.error import HTTPError, URLError
   
   from djmoney.contrib.exchange.backends.base import SimpleExchangeBackend
   
  @@ -26,4 +27,8 @@
   
           symbols = ','.join(currency_codes())
   
  -        super().update_rates(base=base_currency, symbols=symbols)
  +        try:
  +            super().update_rates(base=base_currency, symbols=symbols)
  +        # catch connection errors
  +        except (HTTPError, URLError):
  +            print('Encountered connection error while updating')
  
verification_info: {"golden_diff": "diff --git a/InvenTree/InvenTree/exchange.py b/InvenTree/InvenTree/exchange.py\n--- a/InvenTree/InvenTree/exchange.py\n+++ b/InvenTree/InvenTree/exchange.py\n@@ -1,4 +1,5 @@\n from common.settings import currency_code_default, currency_codes\n+from urllib.error import HTTPError, URLError\n \n from djmoney.contrib.exchange.backends.base import SimpleExchangeBackend\n \n@@ -26,4 +27,8 @@\n \n         symbols = ','.join(currency_codes())\n \n-        super().update_rates(base=base_currency, symbols=symbols)\n+        try:\n+            super().update_rates(base=base_currency, symbols=symbols)\n+        # catch connection errors\n+        except (HTTPError, URLError):\n+            print('Encountered connection error while updating')\n", "issue": "Can't start inventree server\nIt seems that error at `https://api.exchangerate.host/latest` blocks server startup.\r\n\r\n```\r\n# curl https://api.exchangerate.host/latest\r\n<html>\r\n<head><title>521 Origin Down</title></head>\r\n<body bgcolor=\"white\">\r\n<center><h1>521 Origin Down</h1></center>\r\n<hr><center>cloudflare-nginx</center>\r\n</body>\r\n</html>\r\n```\r\n\r\n<details>\r\n\r\n```\r\n# inv server\r\nInvenTree Database Configuration\r\n================================\r\nENGINE: django.db.backends.mysql\r\nNAME: inventree\r\nHOST: localhost\r\nBase currency changed from USD to RUB\r\nUpdating exchange rates from https://api.exchangerate.host/latest\r\nUsing base currency 'RUB'\r\nInvenTree Database Configuration\r\n================================\r\nENGINE: django.db.backends.mysql\r\nNAME: inventree\r\nHOST: localhost\r\nBase currency changed from USD to RUB\r\nUpdating exchange rates from https://api.exchangerate.host/latest\r\nUsing base currency 'RUB'\r\nWatching for file changes with StatReloader\r\nWatching for file changes with StatReloader\r\nException in thread django-main-thread:\r\nTraceback (most recent call last):\r\n  File \"/usr/lib64/python3.6/threading.py\", line 916, in _bootstrap_inner\r\n    self.run()\r\n  File \"/usr/lib64/python3.6/threading.py\", line 864, in run\r\n    self._target(*self._args, **self._kwargs)\r\n  File \"/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/utils/autoreload.py\", line 64, in wrapper\r\n    fn(*args, **kwargs)\r\n  File \"/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/core/management/commands/runserver.py\", line 110, in inner_run\r\n    autoreload.raise_last_exception()\r\n  File \"/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/utils/autoreload.py\", line 87, in raise_last_exception\r\n    raise _exception[1]\r\n  File \"/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/core/management/__init__.py\", line 375, in execute\r\n    autoreload.check_errors(django.setup)()\r\n  File \"/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/utils/autoreload.py\", line 64, in wrapper\r\n    fn(*args, **kwargs)\r\n  File \"/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/__init__.py\", line 24, in setup\r\n    apps.populate(settings.INSTALLED_APPS)\r\n  File \"/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/django/apps/registry.py\", line 122, in populate\r\n    app_config.ready()\r\n  File \"/var/projects/inventree/inventree/InvenTree/InvenTree/apps.py\", line 24, in ready\r\n    self.update_exchange_rates()\r\n  File \"/var/projects/inventree/inventree/InvenTree/InvenTree/apps.py\", line 105, in update_exchange_rates\r\n    update_exchange_rates()\r\n  File \"/var/projects/inventree/inventree/InvenTree/InvenTree/tasks.py\", line 199, in update_exchange_rates\r\n    backend.update_rates(base_currency=base)\r\n  File \"/var/projects/inventree/inventree/InvenTree/InvenTree/exchange.py\", line 29, in update_rates\r\n    super().update_rates(base=base_currency, symbols=symbols)\r\n  File \"/usr/lib64/python3.6/contextlib.py\", line 52, in inner\r\n    return func(*args, **kwds)\r\n  File \"/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/djmoney/contrib/exchange/backends/base.py\", line 68, in update_rates\r\n    for currency, value in self.get_rates(**params).items()\r\n  File \"/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/djmoney/contrib/exchange/backends/base.py\", line 80, in get_rates\r\n    response = self.get_response(**params)\r\n  File \"/var/projects/inventree/inventree-env/lib64/python3.6/site-packages/djmoney/contrib/exchange/backends/base.py\", line 48, in get_response\r\n    response = urlopen(url, cafile=certifi.where())\r\n  File \"/usr/lib64/python3.6/urllib/request.py\", line 223, in urlopen\r\n    return opener.open(url, data, timeout)\r\n  File \"/usr/lib64/python3.6/urllib/request.py\", line 532, in open\r\n    response = meth(req, response)\r\n  File \"/usr/lib64/python3.6/urllib/request.py\", line 642, in http_response\r\n    'http', request, response, code, msg, hdrs)\r\n  File \"/usr/lib64/python3.6/urllib/request.py\", line 570, in error\r\n    return self._call_chain(*args)\r\n  File \"/usr/lib64/python3.6/urllib/request.py\", line 504, in _call_chain\r\n    result = func(*args)\r\n  File \"/usr/lib64/python3.6/urllib/request.py\", line 650, in http_error_default\r\n    raise HTTPError(req.full_url, code, msg, hdrs, fp)\r\nurllib.error.HTTPError: HTTP Error 521: Origin Down\r\n```\r\n\r\n</details>\n", "before_files": [{"content": "from common.settings import currency_code_default, currency_codes\n\nfrom djmoney.contrib.exchange.backends.base import SimpleExchangeBackend\n\n\nclass InvenTreeExchange(SimpleExchangeBackend):\n    \"\"\"\n    Backend for automatically updating currency exchange rates.\n\n    Uses the exchangerate.host service API\n    \"\"\"\n\n    name = \"InvenTreeExchange\"\n\n    def __init__(self):\n        self.url = \"https://api.exchangerate.host/latest\"\n\n        super().__init__()\n\n    def get_params(self):\n        # No API key is required\n        return {\n        }\n\n    def update_rates(self, base_currency=currency_code_default()):\n\n        symbols = ','.join(currency_codes())\n\n        super().update_rates(base=base_currency, symbols=symbols)\n", "path": "InvenTree/InvenTree/exchange.py"}]}