rarray: bound spacings to greater than 0 (#454)

* rarray: bound spacings to greater than 0
This addresses Issue 451

* Fix a typo. (#452)

* Fix a typo.

* Pin black version in travis

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

* rarray: bound spacings to greater than 0
This addresses Issue 451

* Added test for rarray error handling

Co-authored-by: Kevin Menard <kevin@nirvdrum.com>
Co-authored-by: Adam Urbańczyk <adam-urbanczyk@users.noreply.github.com>

cadquery/cq.py

@@ -1291,7 +1291,7 @@ def rarray(
             false, the lower left corner will be at the center of the work plane
         """
 
-        if xSpacing < 1 or ySpacing < 1 or xCount < 1 or yCount < 1:
+        if xSpacing <= 0 or ySpacing <= 0 or xCount < 1 or yCount < 1:
             raise ValueError("Spacing and count must be > 0 ")
 
         lpoints = []  # coordinates relative to bottom left point

tests/test_cadquery.py

@@ -8,7 +8,7 @@
 from random import random
 from random import randrange
 
-from pytest import approx
+from pytest import approx, raises
 
 # my modules
 
@@ -960,6 +960,9 @@ def testRectArray(self):
         # 6 faces for the box, 2 faces for each cylinder
         self.assertEqual(6 + NUMX * NUMY * 2, s.faces().size())
 
+        with raises(ValueError):
+            Workplane().rarray(0, 0, NUMX, NUMY, True)
+
     def testPolarArray(self):
         radius = 10