compiler: Fix the kw argument needs value exception

Strip the \ufdd0 prefix from the keyword argument before turning it into
a string: the same representation the user entered looks better, and is
printable too, thus Python2 doesn't choke on it.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

hy/compiler.py

@@ -461,7 +461,7 @@ class HyASTCompiler(object):
                 except StopIteration:
                     raise HyTypeError(expr,
                                       "Keyword argument {kw} needs "
-                                      "a value.".format(kw=str(expr)))
+                                      "a value.".format(kw=str(expr[1:])))
 
                 compiled_value = self.compile(value)
                 ret += compiled_value

tests/compilers/test_ast.py

@@ -444,7 +444,7 @@ def test_missing_keyword_argument_value():
     try:
         can_compile("((fn [x] x) :x)")
     except HyTypeError as e:
-        assert(e.message == "Keyword argument \ufdd0:x needs a value.")
+        assert(e.message == "Keyword argument :x needs a value.")
     else:
         assert(False)