Fixed another instance of Python 2.7 backwards compatibility for list copying

Author: lindonroberts

dfols/trust_region.py

@@ -109,7 +109,7 @@ def ctrsbox(xopt, g, H, projections, delta, d_max_iters=100, d_tol=1e-10, use_fo
     trproj = lambda w: pball(w, xopt, delta)
 
     # combine trust region constraints with user-entered constraints
-    P = projections.copy()
+    P = list(projections)  # make a copy of the projections list
     P.append(trproj)
     def proj(d0):
         p = dykstra(P, xopt+d0, max_iter=d_max_iters, tol=d_tol)