raise error when trying to run Xvfb on Mac. close #1400

Author: oesteban

nipype/utils/config.py

@@ -11,6 +11,7 @@
 '''
 from __future__ import print_function, division, unicode_literals, absolute_import
 import os
+import sys
 import errno
 import atexit
 from warnings import warn
@@ -284,6 +285,14 @@ def _mock():
             self._display = Xvfb(ndisp, _mock)
             return sysdisplay
         else:
+            if 'darwin' in sys.platform:
+                raise RuntimeError(
+                    'Xvfb requires root permissions to run in OSX. Please '
+                    'make sure that an X server is listening and set the '
+                    'appropriate config on either $DISPLAY or nipype\'s '
+                    '"display_variable" config. Valid X servers include '
+                    'VNC, XQuartz, or manually started Xvfb.')
+
             # If $DISPLAY is empty, it confuses Xvfb so unset
             if sysdisplay == '':
                 del os.environ['DISPLAY']

nipype/utils/tests/test_config.py

@@ -108,3 +108,15 @@ def test_display_empty_installed(monkeypatch):
         config._config.remove_option('execution', 'display_variable')
     monkeypatch.setitem(os.environ, 'DISPLAY', '')
     assert int(config.get_display().split(':')[-1]) > 1000
+
+
+def test_display_empty_macosx(monkeypatch):
+    """Check that when no display is specified, a virtual Xvfb is used"""
+    config._display = None
+    if config.has_option('execution', 'display_variable'):
+        config._config.remove_option('execution', 'display_variable')
+    monkeypatch.delitem(os.environ, 'DISPLAY', '')
+
+    monkeypatch.setattr(sys, 'platform', 'darwin')
+    with pytest.raises(RuntimeError):
+        config.get_display()