Docs builds failing

[jaraco]

The docs builds are failing with a host of warnings:

WARNING: error while formatting arguments for cssutils.css.CSSStyleSheet.namespaces: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSStyleSheet.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSRule.parent: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSRule.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSRuleList.length: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSCharsetRule.parent: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSCharsetRule.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSFontFaceRule.parent: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSFontFaceRule.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSImportRule.parent: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSImportRule.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSMediaRule.name: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSMediaRule.parent: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSMediaRule.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSNamespaceRule.parent: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSNamespaceRule.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSPageRule.parent: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSPageRule.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.MarginRule.parent: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.MarginRule.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSStyleRule.parent: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSStyleRule.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSVariablesRule.parent: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSVariablesRule.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSComment.parent: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSComment.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.Selector.element: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.Selector.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSVariablesDeclaration.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSStyleDeclaration.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.Property.priority: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.PropertyValue.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.Value.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.ColorValue.alpha: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.ColorValue.blue: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.ColorValue.green: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.ColorValue.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.ColorValue.type: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.DimensionValue.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.URIValue.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSFunction.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSCalc.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSVariable.fallback: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.CSSVariable.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.css.MSValue.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.profiles.Profiles.knownNames: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.stylesheets.StyleSheet.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.stylesheets.MediaQuery.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))
WARNING: error while formatting arguments for cssutils.stylesheets.MediaList.seq: Handler <function update_defvalue at 0x10614c0e0> for event 'autodoc-before-process-signature' threw an exception (exception: invalid syntax. Maybe you meant '==' or ':=' instead of '='? (<unknown>, line 2))

[jaraco]

Its not obvious to me what those errors mean or how to fix them, but they're blocking CI.