Face.makeFromWires - check that wires are closed

[lorenzncode]

This is to resolve #944. The segfault occurs when the outer wire is open and inner wires exist.

An exception (for now?) to the closed wire check is the outer wire need not be closed if inner wires is empty. Existing tests rely on this (Wire.fillet2D, chamfer2D).

Example of an open outer wire that would still be allowed:

s = (
    cq.Sketch()
    .segment((0, 0), (0, 1.0))
    .segment((0, 1.0), (1.0, 1.0))
    .assemble()
)

r = cq.Workplane().placeSketch(s).extrude(0.1)

DXF import previously could result in the following when the inner wire was not closed:

With the inner wire IsClosed() check, the DXF import results in ValueError with message:

  File "/home/lorenzn/devel/cadquery/cadquery/occ_impl/shapes.py", line 2280, in makeFromWires
    raise ValueError("Cannot build face(s): inner wire is not closed")
ValueError: Cannot build face(s): inner wire is not closed

[codecov]

Codecov Report

Merging #946 (9097fe0) into master (9ef08d6) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #946      +/-   ##
==========================================
+ Coverage   96.06%   96.07%   +0.01%     
==========================================
  Files          39       39              
  Lines        9207     9233      +26     
  Branches     1109     1111       +2     
==========================================
+ Hits         8845     8871      +26     
  Misses        209      209              
  Partials      153      153              

Impacted Files	Coverage Δ
cadquery/occ_impl/shapes.py	92.54% <100.00%> (+0.02%)	⬆️
tests/test_cadquery.py	99.27% <100.00%> (+<0.01%)	⬆️
tests/test_importers.py	94.59% <100.00%> (ø)
tests/test_sketch.py	100.00% <100.00%> (ø)

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[jmwright]

Thanks @lorenzncode !