add G₂ to classify_root_system

src/roots.jl

@@ -90,7 +90,6 @@ function classify_root_system(
         elseif b == 1 && c == 2
             return :C₂
         elseif b == 1 && c == 3
-            @warn ":G₂? really?"
             return :G₂
         else
             @error a, b, c, d
@@ -170,8 +169,11 @@ function classify_sub_root_system(
         if :C₂ in subtypes
             return :C₂
         end
+        @warn subtypes
+    elseif l == 6
+        return :G₂
     end
-    @error "Unknown root subsystem generated by" α β
+    @error "Unknown root subsystem generated by" α β l
     throw("Unknown root system: $subsystem")
 end