Pass download lock between xdist workers

oggm/tests/conftest.py

@@ -0,0 +1,22 @@
+import pytest
+import multiprocessing as mp
+from oggm import utils
+from random import randint
+
+global_lock = mp.Manager().Lock()
+
+class OggmMpLockPlugin():
+    def pytest_configure(config):
+        if hasattr(config, 'slaveinput'):
+            print("In Slave: %s" % config.workerinput['shared_lock'])
+        else:
+            config.shared_lock = randint(0, 100)
+            print("In Master: %s" % config.shared_lock)
+
+    def pytest_configure_node(node):
+        node.workerinput['shared_lock'] = node.config.shared_lock
+
+def pytest_configure(config):
+    if config.pluginmanager.hasplugin('xdist'):
+        config.pluginmanager.register(OggmMpLockPlugin())
+