Bugfix for passing default arguments to GSI calls

This happens when default arguments (specifically
user class or enum types) and passed between keyword
and positional arguments. We must not use a temporary
tl::Variant object as it gets out of scope and a
reference is stored.

In addition: better error messages for Python when
a method can't be matched to arguments.

testdata/ruby/basic_testcore.rb

@@ -3154,4 +3154,51 @@ class Basic_TestClass < TestBase
 
   end
 
+  # keyword arguments, enums and error messages
+  def test_81
+
+    bb = RBA::BB::new
+    
+    m = ""
+    begin
+      bb.d4()
+    rescue => ex
+      m = ex.to_s
+    end
+    assert_equal(m, "Can't match arguments. Variants are:\n  string d4(int a, string b, double c, B3::E d = E3A, variant e = nil) [no value given for argument #1 and following]\n in BB.d4")
+
+    m = ""
+    begin
+      bb.d4(1, "a")
+    rescue => ex
+      m = ex.to_s
+    end
+    assert_equal(m, "Can't match arguments. Variants are:\n  string d4(int a, string b, double c, B3::E d = E3A, variant e = nil) [no value given for argument #3]\n in BB.d4")
+
+    m = ""
+    begin
+      bb.d4(1, "a", 2.0, xxx=17)
+    rescue => ex
+      m = ex.to_s
+    end
+    assert_equal(m, "Unknown keyword parameter: xxx in BB.d4")
+
+    m = ""
+    begin
+      bb.d4(a=1, b="a", c=2.0, xxx=17)
+    rescue => ex
+      m = ex.to_s
+    end
+    assert_equal(m, "Unknown keyword parameter: xxx in BB.d4")
+
+    assert_equal(bb.d4(1, "a", 2.0), "1,a,2,100,nil")
+    assert_equal(bb.d4(1, "a", 2.0, e=42), "1,a,2,100,42")
+    assert_equal(bb.d4(1, "a", c=2.0, e=42), "1,a,2,100,42")
+    assert_equal(bb.d4(c=2.0, a=1, b="a", e=42), "1,a,2,100,42")
+    assert_equal(bb.d4(1, "a", 2.0, d=RBA::BB::E::E3B), "1,a,2,101,nil")
+    assert_equal(bb.d4(1, "a", d=RBA::BB::E::E3B, c=2.5), "1,a,2.5,101,nil")
+    assert_equal(bb.d4(1, "a", 2.0, RBA::BB::E::E3B, 42), "1,a,2,101,42")
+
+  end
+
 end