builder: variable doesn't build but output message is still  kindda positive
Recently we allowed the variable build to fail without stopping the build, but it still yeld "Completed" at the end.


```
ERROR:cu2qu.ufo:Glyphs named 'gcommaaccent' have different number of segments
ERROR:GFBuilder:Could not build variable font: In 'Anybody.glyphs' -> 'master_ufo/Anybody.designspace': Generating fonts from Designspace failed: fonts contains incompatible glyphs: 'gcommaaccent'
INFO:GFBuilder:Building variable completed. All done!
```
diff --git a/Lib/gftools/builder/__init__.py b/Lib/gftools/builder/__init__.py
index 32e8aea..58adeba 100644
--- a/Lib/gftools/builder/__init__.py
+++ b/Lib/gftools/builder/__init__.py
@@ -291,13 +291,10 @@ class GFBuilder:
             args["output_path"] = os.path.join(
                 self.config["vfDir"], sourcebase + "-VF.ttf",
             )
-            try:
-                output_files = self.run_fontmake(source, args)
-                newname = self.rename_variable(output_files[0])
-                ttFont = TTFont(newname)
-                ttFonts.append(ttFont)
-            except Exception as e:
-                self.logger.error("Could not build variable font: %s" % e)
+            output_files = self.run_fontmake(source, args)
+            newname = self.rename_variable(output_files[0])
+            ttFont = TTFont(newname)
+            ttFonts.append(ttFont)
 
         if not ttFonts:
             return
['Lib/gftools/builder/__init__.py']