tests: Update test suite to be compatible with CPython 3.6.

CPython 3.6 has a few changes that, when run on uPy's test suite, give a
different output to CPython 3.5.  uPy currently officially supports the
3.4 language definition, but it's useful to be able to run the test suite
with 3.4/3.5/3.6 versions of CPython.  This patch makes such changes to
support 3.6.

tests/basics/python34.py

@@ -1,4 +1,4 @@
-# tests that differ when running under Python 3.4 vs 3.5
+# tests that differ when running under Python 3.4 vs 3.5/3.6
 
 # from basics/fun_kwvarargs.py
 # test evaluation order of arguments (in 3.4 it's backwards, 3.5 it's fixed)
@@ -13,14 +13,15 @@ f4(*print_ret(['a', 'b']), kw_arg=print_ret(None))
 {print_ret(1):print_ret(2)}
 
 # from basics/syntaxerror.py
-# can't have multiple * or ** (in 3.5 we can)
 def test_syntax(code):
     try:
         exec(code)
     except SyntaxError:
         print("SyntaxError")
-test_syntax("f(*a, *b)")
-test_syntax("f(**a, **b)")
+test_syntax("f(*a, *b)") # can't have multiple * (in 3.5 we can)
+test_syntax("f(**a, **b)") # can't have multiple ** (in 3.5 we can)
+test_syntax("() = []") # can't assign to empty tuple (in 3.6 we can)
+test_syntax("del ()") # can't delete empty tuple (in 3.6 we can)
 
 # from basics/sys1.py
 # uPy prints version 3.4

tests/basics/python34.py.exp

@@ -5,5 +5,7 @@ None
 1
 SyntaxError
 SyntaxError
+SyntaxError
+SyntaxError
 3.4
 3 4

tests/basics/syntaxerror.py

@@ -46,9 +46,6 @@ test_syntax("f**2 = 1")
 # can't assign to power of composite
 test_syntax("f[0]**2 = 1")
 
-# can't assign to empty tuple
-test_syntax("() = 1")
-
 # can't have *x on RHS
 test_syntax("x = *x")
 
@@ -66,7 +63,6 @@ test_syntax("[a, b] += c")
 test_syntax("def f(a=1, b): pass")
 
 # can't delete these things
-test_syntax("del ()")
 test_syntax("del f()")
 test_syntax("del f[0]**2")
 test_syntax("del (a for a in a)")