Find inherited stylesheet

ntd2d/ntd2d_action/files/templates/ntd2d/static/ntd2d.css_t

@@ -1,4 +1,4 @@
-@import url("{inherited_theme}.css");
+@import url("{inherited_css}");
 
 
 .dropbtn {{

ntd2d/ntd2d_action/sphinxdocs.py

@@ -8,6 +8,8 @@
 import pathlib
 import shlex
 import shutil
+from sphinx.application import Sphinx
+from sphinx.theming import HTMLThemeFactory
 import subprocess
 import tempfile
 
@@ -45,6 +47,18 @@ def epub_file(self):
     def pdf_file(self):
         return self.build_dir / "latex" / f"{self.conf.project.lower()}.pdf"
 
+    @property
+    def stylesheet(self):
+        app = Sphinx(srcdir=self.source_dir,
+                     confdir=self.source_dir,
+                     outdir=self.build_dir,
+                     doctreedir=self.build_dir / "doctrees",
+                     buildername="html")
+        theme_factory = HTMLThemeFactory(app)
+        theme = theme_factory.create(app.config.html_theme)
+
+        return theme.get_config("theme", "stylesheet")
+
     def build_docs(self, build_command):
         """Build Sphinx Documentation
 
@@ -129,7 +143,8 @@ def assimilate_theme(self, name):
 
         self.theme = TemplateHierarchy(name=name,
                                        destination_dir=self.conf.theme_path,
-                                       inherited_theme=self.inherited_theme)
+                                       inherited_theme=self.inherited_theme,
+                                       inherited_css=self.stylesheet)
         self.theme.write()
 
         self.conf.set_html_theme(name=name)