Fix test_tsfresh: skip when tsfresh import fails on CPU

tsfresh -> stumpy -> numba.cuda, which requires libcudart.so.
Guard the import so the test is skipped on CPU rather than crashing.

Author: stevemessick

tests/test_tsfresh.py

@@ -3,8 +3,13 @@
 import pandas as pd
 import numpy as np
 
-from tsfresh import extract_features
+try:
+    from tsfresh import extract_features
+    HAS_TSFRESH = True
+except ImportError:
+    HAS_TSFRESH = False
 
+@unittest.skipUnless(HAS_TSFRESH, 'tsfresh is not importable (may require CUDA libs)')
 class TestTsFresh(unittest.TestCase):
     def test_extract_feature(self):
         ts = pd.DataFrame({
@@ -14,5 +19,3 @@ def test_extract_feature(self):
         })
         extracted_features = extract_features(ts, column_id='id', column_sort='time', n_jobs=1)
         self.assertEqual(2, len(extracted_features))
-
-