Fix build

Author: ptomecek

.github/workflows/build.yml

@@ -672,6 +672,7 @@ jobs:
           package:
             - "sqlalchemy<2"
             - "numpy==1.19.5"
+            - "pandas<2"
             - "perspective-python<3"
 
       runs-on: ${{ matrix.os }}

csp/tests/adapters/test_perspective.py

@@ -1,9 +1,14 @@
+import unittest
 from datetime import date, datetime, timedelta
 
 import csp
-from csp.adapters.perspective import PerspectiveAdapter
-from csp.impl.pandas_perspective import CspPerspectiveMultiTable, CspPerspectiveTable
-from csp.impl.perspective_common import PerspectiveWidget, is_perspective3
+
+try:
+    from csp.adapters.perspective import PerspectiveAdapter
+    from csp.impl.pandas_perspective import CspPerspectiveMultiTable, CspPerspectiveTable
+    from csp.impl.perspective_common import PerspectiveWidget, is_perspective3
+except ImportError:
+    raise unittest.SkipTest("skipping perspective tests")
 
 _PERSPECTIVE_3 = is_perspective3()
 
@@ -26,7 +31,7 @@ def my_graph(output={}):
     output["table"] = table
 
 
-class TestPerspectiveAdapter:
+class TestPerspectiveAdapter(unittest.TestCase):
     def test_adapter(self):
         output = {}
         csp.run(my_graph, output, starttime=datetime.utcnow(), endtime=timedelta(seconds=1))