test case for tuple unpacking of a list comprehension

tests/run/unpacklistcomp.pyx

+__doc__ = """
+    >>> unpack_normal([1,2])
+    (1, 2)
+    >>> unpack_normal([1,2,3])
+    Traceback (most recent call last):
+    ValueError: too many values to unpack
+
+    >>> unpack_comp([1,2])
+    (1, 2)
+    >>> unpack_comp([1,2,3])
+    Traceback (most recent call last):
+    ValueError: too many values to unpack
+
+    >>> unpack_expr([1,2])
+    (1, 2)
+    >>> unpack_expr([1,2,3])
+    Traceback (most recent call last):
+    ValueError: too many values to unpack
+"""
+
+def unpack_normal(l):
+    a,b = l
+    return a,b
+
+def unpack_comp(l):
+    a,b = [ n for n in l ]
+    return a,b
+
+def unpack_expr(l):
+    a,b = [ n*n for n in l ]
+    return a,b