Part: expose Geom2dCircle::getCircleCenter to Python and fix a regression

src/Mod/Part/App/Geom2d/Circle2dPy.xml

@@ -31,6 +31,11 @@ Part.Geom2d.Circle2d(Point1,Point2,Point3)
     Creates a circle defined by three non-linear points
    </UserDocu>
     </Documentation>
+    <Methode Name="getCircleCenter" Static="true">
+      <Documentation>
+        <UserDocu>Get the circle center defined by three points</UserDocu>
+      </Documentation>
+    </Methode>
     <Attribute Name="Radius" ReadOnly="false">
       <Documentation>
         <UserDocu>The radius of the circle.</UserDocu>

src/Mod/Part/App/Geom2d/Circle2dPyImp.cpp

@@ -143,6 +143,24 @@ int Circle2dPy::PyInit(PyObject* args, PyObject* kwds)
     return -1;
 }
 
+PyObject* Circle2dPy::getCircleCenter(PyObject *args)
+{
+    PyObject* p1;
+    PyObject* p2;
+    PyObject* p3;
+    if (!PyArg_ParseTuple(args, "O!O!O!", Base::Vector2dPy::type_object(), &p1
+                                        , Base::Vector2dPy::type_object(), &p2
+                                        , Base::Vector2dPy::type_object(), &p3))
+        return nullptr;
+
+    Base::Vector2d v1 = Py::toVector2d(p1);
+    Base::Vector2d v2 = Py::toVector2d(p2);
+    Base::Vector2d v3 = Py::toVector2d(p3);
+
+    Base::Vector2d cnt = Geom2dCircle::getCircleCenter(v1, v2, v3);
+    return Py::new_reference_to(Base::Vector2dPy::create(cnt));
+}
+
 Py::Float Circle2dPy::getRadius(void) const
 {
     Handle(Geom2d_Circle) circle = Handle(Geom2d_Circle)::DownCast(getGeom2dCirclePtr()->handle());

src/Mod/Part/App/Geometry2d.cpp

@@ -932,7 +932,8 @@ Base::Vector2d Geom2dCircle::getCircleCenter (const Base::Vector2d &p1, const Ba
     double vv =  v*v;
     double ww =  w*w;
 
-    if (abs(uu * vv * ww) < Precision::Confusion())
+    double eps2 = Precision::SquareConfusion();
+    if (uu < eps2 || vv < eps2 || ww < eps2)
         THROWM(Base::ValueError,"Two points are coincident");
 
     double uv = -(u*v);
@@ -945,7 +946,7 @@ Base::Vector2d Geom2dCircle::getCircleCenter (const Base::Vector2d &p1, const Ba
 
     double wx = w0 + w1 + w2;
 
-    if( abs(wx) < Precision::Confusion())
+    if (abs(wx) < Precision::Confusion())
         THROWM(Base::ValueError,"Points are collinear");
 
     double x = (w0*p1.x + w1*p2.x + w2*p3.x)/wx;