Merge pull request #51 from minrk/ruamel-hint

raise informative error when ruamel.yaml is missing due to ruamel_yaml

jupyter_telemetry/eventlog.py

@@ -7,7 +7,23 @@
 
 import jsonschema
 from pythonjsonlogger import jsonlogger
-from ruamel.yaml import YAML
+try:
+    from ruamel.yaml import YAML
+except ImportError as e:
+    # check for known conda bug that prevents
+    # pip from installing ruamel.yaml dependency
+    try:
+        import ruamel_yaml  # noqa
+    except ImportError:
+        # nope, regular import error; raise original
+        raise e
+    else:
+        # have conda fork ruamel_yaml, but not ruamel.yaml.
+        # this is a bug in the ruamel_yaml conda package
+        # mistakenly identifying itself as ruamel.yaml to pip.
+        # conda install the 'real' ruamel.yaml to fix
+        raise ImportError("Missing dependency ruamel.yaml. Try: `conda install ruamel.yaml`")
+
 from traitlets import List
 from traitlets.config import Configurable, Config