Errors printed in admonitions instead of plaintext for html with hdl_diagram

Signed-off-by: Michael Riegert <michael@eowyn.net>

Author: nobodywasishere

sphinxcontrib_hdl_diagrams/__init__.py

@@ -421,7 +421,7 @@ def render_diagram(self, code, options, format, skin, yosys_script):
         module = options['module']
     elif source_ext == '.vhd' or source_ext == '.vhdl':
         if yosys == "yowasp":
-            raise HDLDiagramError("Cannot use YoWASP for VHDL")
+            raise HDLDiagramError("Cannot use YoWASP for VHDL (yet)")
         module = options['module']
         ilfn = path.join(self.builder.outdir, self.builder.imagedir, options['outname'] + '.v')
         vhdl_to_verilog(source_path, ilfn, module, self.builder.config.hdl_diagram_ghdl, yosys)
@@ -499,8 +499,10 @@ def render_diagram_html(
         # raise nodes.SkipNode
 
     if diagram_error:
-        self.body.append("WARNING: hdl_diagram code '{file}': {err}".format(
-                        file=self.encode(code).strip(), err=diagram_error_message))
+        self.body.append('<div class="admonition warning">'
+            '<paragraph class="admonition-title">{title}: </paragraph>'
+            '<paragraph>hdl_diagram code <code>{file}</code>: {message}</paragraph>'
+            '</div>'.format(title="Warning", file=code, message=diagram_error_message))
     elif fname is None:
         self.body.append(self.encode(code))
     else: