Fix ValueError popping out in sphinx.ext.napoleon.

sphinx/ext/napoleon/docstring.py

@@ -46,7 +46,11 @@
 
 
 class Deque(collections.deque):
-    """A subclass of deque with an additional `.Deque.get` method."""
+    """
+    A subclass of deque that mimics ``pockets.iterators.modify_iter``.
+
+    The `.Deque.get` and `.Deque.next` methods are added.
+    """
 
     sentinel = object()
 
@@ -57,6 +61,12 @@ def get(self, n: int) -> Any:
         """
         return self[n] if n < len(self) else self.sentinel
 
+    def next(self) -> Any:
+        if self:
+            return super().popleft()
+        else:
+            raise StopIteration
+
 
 def _convert_type_spec(_type: str, translations: Dict[str, str] = {}) -> str:
     """Convert type specification to reference in reST."""
@@ -240,7 +250,7 @@ def _consume_indented_block(self, indent: int = 1) -> List[str]:
         line = self._lines.get(0)
         while(not self._is_section_break() and
               (not line or self._is_indented(line, indent))):
-            lines.append(self._lines.popleft())
+            lines.append(self._lines.next())
             line = self._lines.get(0)
         return lines
 
@@ -249,20 +259,20 @@ def _consume_contiguous(self) -> List[str]:
         while (self._lines and
                self._lines.get(0) and
                not self._is_section_header()):
-            lines.append(self._lines.popleft())
+            lines.append(self._lines.next())
         return lines
 
     def _consume_empty(self) -> List[str]:
         lines = []
         line = self._lines.get(0)
         while self._lines and not line:
-            lines.append(self._lines.popleft())
+            lines.append(self._lines.next())
             line = self._lines.get(0)
         return lines
 
     def _consume_field(self, parse_type: bool = True, prefer_type: bool = False
                        ) -> Tuple[str, str, List[str]]:
-        line = self._lines.popleft()
+        line = self._lines.next()
 
         before, colon, after = self._partition_field_on_colon(line)
         _name, _type, _desc = before, '', after
@@ -300,7 +310,7 @@ def _consume_fields(self, parse_type: bool = True, prefer_type: bool = False,
         return fields
 
     def _consume_inline_attribute(self) -> Tuple[str, List[str]]:
-        line = self._lines.popleft()
+        line = self._lines.next()
         _type, colon, _desc = self._partition_field_on_colon(line)
         if not colon or not _desc:
             _type, _desc = _desc, _type
@@ -338,7 +348,7 @@ def _consume_usage_section(self) -> List[str]:
         return lines
 
     def _consume_section_header(self) -> str:
-        section = self._lines.popleft()
+        section = self._lines.next()
         stripped_section = section.strip(':')
         if stripped_section.lower() in self._sections:
             section = stripped_section
@@ -347,14 +357,14 @@ def _consume_section_header(self) -> str:
     def _consume_to_end(self) -> List[str]:
         lines = []
         while self._lines:
-            lines.append(self._lines.popleft())
+            lines.append(self._lines.next())
         return lines
 
     def _consume_to_next_section(self) -> List[str]:
         self._consume_empty()
         lines = []
         while not self._is_section_break():
-            lines.append(self._lines.popleft())
+            lines.append(self._lines.next())
         return lines + self._consume_empty()
 
     def _dedent(self, lines: List[str], full: bool = False) -> List[str]:
@@ -1170,7 +1180,7 @@ def _escape_args_and_kwargs(self, name: str) -> str:
 
     def _consume_field(self, parse_type: bool = True, prefer_type: bool = False
                        ) -> Tuple[str, str, List[str]]:
-        line = self._lines.popleft()
+        line = self._lines.next()
         if parse_type:
             _name, _, _type = self._partition_field_on_colon(line)
         else:
@@ -1201,10 +1211,10 @@ def _consume_returns_section(self, preprocess_types: bool = False
         return self._consume_fields(prefer_type=True)
 
     def _consume_section_header(self) -> str:
-        section = self._lines.popleft()
+        section = self._lines.next()
         if not _directive_regex.match(section):
             # Consume the header underline
-            self._lines.popleft()
+            self._lines.next()
         return section
 
     def _is_section_break(self) -> bool: