Address minor numpy deprecation (#2856)

* address numpy deprecation

* add match to pytest.raises

Author: kandersolar

tests/test_clearsky.py

@@ -663,9 +663,10 @@ def test_detect_clearsky_arrays(detect_clearsky_data):
 def test_detect_clearsky_irregular_times(detect_clearsky_data):
     expected, cs = detect_clearsky_data
     times = cs.index.values.copy()
-    times[0] += 10**9
+    times[0] += pd.Timedelta(1, unit='s')
     times = pd.DatetimeIndex(times)
-    with pytest.raises(NotImplementedError):
+    match = "does not yet support unequal time intervals"
+    with pytest.raises(NotImplementedError, match=match):
         clearsky.detect_clearsky(expected['GHI'].values, cs['ghi'].values,
                                  times, 10)