refactor(numpy): patch modern flip function for versions older than 1…

….15.0 (#1004)

flopy/discretization/structuredgrid.py

@@ -2,6 +2,34 @@
 import numpy as np
 from .grid import Grid, CachedData
 
+try:
+    from numpy.lib import NumpyVersion
+
+    numpy115 = NumpyVersion(np.__version__) >= "1.15.0"
+except ImportError:
+    numpy115 = False
+
+if not numpy115:
+
+    def flip_numpy115(m, axis=None):
+        """Provide same behavior for np.flip since numpy 1.15.0."""
+        import numpy.core.numeric as _nx
+        from numpy.core.numeric import asarray
+
+        if not hasattr(m, "ndim"):
+            m = asarray(m)
+        if axis is None:
+            indexer = (np.s_[::-1],) * m.ndim
+        else:
+            axis = _nx.normalize_axis_tuple(axis, m.ndim)
+            indexer = [np.s_[:]] * m.ndim
+            for ax in axis:
+                indexer[ax] = np.s_[::-1]
+            indexer = tuple(indexer)
+        return m[indexer]
+
+    np.flip = flip_numpy115
+
 
 def array_at_verts_basic2d(a):
     """