Pass download lock between xdist workers

oggm/tests/conftest.py

@@ -0,0 +1,22 @@
+import pytest
+import multiprocessing as mp
+from oggm import cfg, utils
+import pickle
+
+class OggmMpLockPlugin():
+    def pytest_configure(config):
+        if hasattr(config, 'workerinput'):
+            utils.lock = pickle.loads(config.workerinput['shared_lock'])
+            cfg.unpack_config(pickle.loads(config.workerinput['shared_cfg']))
+        else:
+            config.shared_lock = mp.Manager().Lock()
+            config.shared_cfg = cfg.pack_config()
+
+    def pytest_configure_node(node):
+        node.workerinput['shared_lock'] = pickle.dumps(node.config.shared_lock)
+        node.workerinput['shared_cfg'] = pickle.dumps(node.config.shared_cfg)
+
+def pytest_configure(config):
+    if config.pluginmanager.hasplugin('xdist'):
+        config.pluginmanager.register(OggmMpLockPlugin())
+