Debug

.travis.yml

@@ -75,6 +75,7 @@ before_install:
 install:
     # Maybe get and clean and patch source
     - clean_code $REPO_DIR $BUILD_COMMIT
+    - git -C pandas apply ../foo.patch
     - build_wheel $REPO_DIR $PLAT
 
 script:

foo.patch

@@ -0,0 +1,35 @@
+diff --git a/pandas/tests/test_downstream.py b/pandas/tests/test_downstream.py
+index 9fe8b0f95..4660da269 100644
+--- a/pandas/tests/test_downstream.py
++++ b/pandas/tests/test_downstream.py
+@@ -135,11 +135,27 @@ def test_pyarrow(df):
+
+ def test_missing_required_dependency():
+     # GH 23868
+-    # use the -S flag to disable site-packages
+-    call = ['python', '-S', '-c', 'import pandas']
++    # To ensure proper isolation, we pass these flags
++    # -S : disable site-packages
++    # -s : disable user site-packages
++    # -E : disable PYTHON* env vars, especially PYTHONPATH
++    # And, that's apparently not enough, so we give up.
++    # https://github.com/MacPython/pandas-wheels/pull/50
++    try:
++        subprocess.check_output(['python', '-sSE', '-c', 'import numpy'],
++                                stderr=subprocess.DEVNULL)
++    except subprocess.CalledProcessError:
++        # NumPy is not around, we can do the test
++        pass
++    else:
++        # NumPy is in the isolation environment, give up.
++        pytest.skip("Required dependencies in isolated environment.")
++
++    call = ['python', '-sSE', '-c', 'import pandas']
+
+     with pytest.raises(subprocess.CalledProcessError) as exc:
+         subprocess.check_output(call, stderr=subprocess.STDOUT)
+
+     output = exc.value.stdout.decode()
+-    assert all(x in output for x in ['numpy', 'pytz', 'dateutil'])
++    for name in ['numpy', 'pytz', 'dateutil']:
++        assert name in output