Fix sketch solver line_point method relative/absolute mixup (#1336)

* Sketch: Fix line_point implementation

Enable assert that fails without the fix ( issue #1127 )

* Change channel order

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Co-authored-by: AU <adam-urbanczyk@users.noreply.github.com>

cadquery/occ_impl/sketch_solver.py

@@ -84,7 +84,7 @@ def arc_point(x, val):
 
 def line_point(x, val):
 
-    return x[:2] + val * x[2:]
+    return x[:2] + val * (x[2:] - x[:2])
 
 
 def arc_first_tangent(x):

tests/test_sketch.py

@@ -640,7 +640,7 @@ def test_constraint_solver():
 
     midpoint = (seg2.startPoint() + seg2.endPoint()) / 2
 
-    (midpoint - seg1.startPoint()).Length == approx(2)
+    assert (midpoint - seg1.startPoint()).Length == approx(2)
 
     s5 = (
         Sketch()