even less error emails and future proofing for test-utils

apps/files/helpers.py

@@ -132,6 +132,13 @@ class FileViewer:
         UTF-8 and UTF-16 files appropriately. Return file contents and
         a list of error messages.
         """
+        try:
+            return self._read_file(allow_empty)
+        except (IOError, OSError):
+            self.selected['msg'] = _('That file no longer exists.')
+            return ''
+
+    def _read_file(self, allow_empty=False):
         if not self.selected and allow_empty:
             return ''
         assert self.selected, 'Please select a file'
@@ -141,12 +148,6 @@ class FileViewer:
             self.selected['msg'] = msg
             return ''
 
-        # Between the file data going into the cache and the file being
-        # accessed, the individual file has been removed.
-        if not os.path.exists(self.selected['full']):
-            self.selected['msg'] = _('That file no longer exists.')
-            return ''
-
         with open(self.selected['full'], 'r') as opened:
             cont = opened.read()
             codec = 'utf-16' if cont.startswith(codecs.BOM_UTF16) else 'utf-8'

apps/files/tests/test_views.py

@@ -66,7 +66,7 @@ class FilesBase:
         # Setting this to True, so we are delaying the extraction of files,
         # in the tests, the files won't be extracted.
         # Most of these tests extract as needed to.
-        Switch.objects.create(name='delay-file-viewer', active=True)
+        Switch.objects.get_or_create(name='delay-file-viewer', active=True)
 
     def tearDown(self):
         self.file_viewer.cleanup()