Improve error message

Author: DilumAluthge

src/forge.jl

@@ -175,7 +175,7 @@ function assert_check_endpoint_url(url::AbstractString)
 
     # Roundtrip the URL through `URIs.resolvereference()`, and make sure it is unchanged
     if url != URIs.resolvereference("https://example.invalid/", url).path
-        throw(ArgumentError("URLs cannot contain path navigation"))
+        throw(ArgumentError("URLs cannot contain path navigation: $(url)"))
     end
 
     return nothing