Remove six.reraise usage

six.reraise can be converted into "raise new_exc from original_exc"
introduced in python3.

In case of horizon.exceptions.handle(), six.reraise was used to
raise the original exception again, so we can convert it into "raise".

six is removed from requirements.txt.
Note that we need to keep six in lower-constraints.txt
as dependent libraries still use six.

Change-Id: I0672a516083727c245f1d4fa5b10eed9cd81a726

horizon/exceptions.py

@@ -20,8 +20,6 @@ import logging
 import os
 import sys
 
-import six
-
 from debtcollector import removals
 from django.core.management import color_style
 from django.utils import encoding
@@ -345,4 +343,6 @@ def handle(request, message=None, redirect=None, ignore=False,
         if ret:
             return ret
 
-    six.reraise(exc_type, exc_value, exc_traceback)
+    # NOTE: This function is intended to call inside an except clause.
+    # pylint: disable=misplaced-bare-raise
+    raise

horizon/tables/base.py

@@ -36,7 +36,6 @@ from django.utils.http import urlencode
 from django.utils.safestring import mark_safe
 from django.utils import termcolors
 from django.utils.translation import ugettext_lazy as _
-import six
 
 from horizon import conf
 from horizon import exceptions
@@ -830,11 +829,8 @@ class Cell(html.HTMLElement):
                     data = self.column.empty_value(self.datum)
                 else:
                     data = self.column.empty_value
-        except Exception:
-            data = None
-            exc_info = sys.exc_info()
-            raise six.reraise(template.TemplateSyntaxError, exc_info[1],
-                              exc_info[2])
+        except Exception as e:
+            raise template.TemplateSyntaxError from e
 
         if self.url and not self.column.auto == "form_field":
             link_attrs = ' '.join(['%s="%s"' % (k, v) for (k, v) in
@@ -1960,13 +1956,11 @@ class DataTable(object, metaclass=DataTableMetaclass):
                     self.selected = True
                     row.classes.append('current_selected')
                 rows.append(row)
-        except Exception:
+        except Exception as e:
             # Exceptions can be swallowed at the template level here,
             # re-raising as a TemplateSyntaxError makes them visible.
             LOG.exception("Error while rendering table rows.")
-            exc_info = sys.exc_info()
-            raise six.reraise(template.TemplateSyntaxError, exc_info[1],
-                              exc_info[2])
+            raise template.TemplateSyntaxError from e
 
         return rows
 

horizon/tables/formset.py

@@ -13,9 +13,6 @@
 import collections
 import itertools
 import logging
-import sys
-
-import six
 
 from django import template
 from django.template import loader
@@ -143,13 +140,11 @@ class FormsetDataTableMixin(object):
                     self.selected = True
                     row.classes.append('current_selected')
                 rows.append(row)
-        except Exception:
+        except Exception as e:
             # Exceptions can be swallowed at the template level here,
             # re-raising as a TemplateSyntaxError makes them visible.
             LOG.exception("Error while rendering table rows.")
-            exc_info = sys.exc_info()
-            raise six.reraise(template.TemplateSyntaxError, exc_info[1],
-                              exc_info[2])
+            raise template.TemplateSyntaxError from e
         return rows
 
     def get_object_id(self, datum):

horizon/tabs/base.py

@@ -15,9 +15,6 @@
 from collections import OrderedDict
 import logging
 import operator
-import sys
-
-import six
 
 from django.conf import settings
 from django.template.loader import render_to_string
@@ -370,9 +367,8 @@ class Tab(html.HTMLElement):
             context = self.data
         except exceptions.Http302:
             raise
-        except Exception:
-            exc_type, exc_value, exc_traceback = sys.exc_info()
-            raise six.reraise(TemplateSyntaxError, exc_value, exc_traceback)
+        except Exception as e:
+            raise TemplateSyntaxError from e
         return render_to_string(self.get_template_name(self.request), context)
 
     def get_id(self):

openstack_dashboard/utils/config_types.py

@@ -18,8 +18,6 @@ import ast
 import os
 import re
 
-import six
-
 from django.utils import encoding
 from django.utils import functional
 from django.utils.module_loading import import_string
@@ -110,7 +108,7 @@ class Literal(types.ConfigType):
             try:
                 value = ast.literal_eval(value)
             except SyntaxError as e:
-                six.raise_from(ValueError(e), e)
+                raise ValueError from e
         self.validate(value, self.spec)
         return self.update(value, self.spec)
 
@@ -205,7 +203,7 @@ class Importable(types.ConfigType):
         try:
             return import_string(value)
         except ImportError as e:
-            six.raise_from(ValueError(e), e)
+            raise ValueError from e
 
     def _formatter(self, value):
         module = value.__module__

requirements.txt

@@ -41,7 +41,6 @@ pytz>=2013.6 # MIT
 PyYAML>=3.12 # MIT
 requests>=2.14.2 # Apache-2.0
 semantic-version>=2.3.1 # BSD
-six>=1.10.0 # MIT
 XStatic>=1.0.0 # MIT License
 XStatic-Angular>=1.5.8.0 # MIT License
 XStatic-Angular-Bootstrap>=2.2.0.0 # MIT License