python: EventLog accept pathlib.Path (#468)

* python: EventLog accept pathlib.Path

* python: Attempt to make pathlib and type args backwards compatible

* python: fix typed union

lcm-python/lcm/__init__.py

@@ -1,4 +1,23 @@
 import os
+import sys
+
+# Attempt to be backwards compatible
+if sys.version_info >= (3, 6):
+    from os import PathLike
+elif sys.version_info >= (3, 4):
+    from pathlib import Path as PathLike
+else:
+    # All we do to the Path is call str on it, so this is a harmless fallback.
+    PathLike = str 
+
+if sys.version_info >= (3, 5):
+    import typing
+    # Not including `bytes` like other APIs in the union as the native interface does not accept a byte string.
+    # Makes more sense for the user to .decode(encoding) the bytes than us.
+    PathArgument = typing.Union[str, PathLike]
+else:
+    PathArgument = object
+
 
 from lcm import _lcm
 from lcm._lcm import LCM, LCMSubscription
@@ -33,7 +52,7 @@ class EventLog(object):
 
 @undocumented: __iter__
     """
-    def __init__ (self, path, mode = "r", overwrite = False):
+    def __init__ (self, path:PathArgument, mode = "r", overwrite = False):
         """
         Initializer
 
@@ -53,6 +72,9 @@ def __init__ (self, path, mode = "r", overwrite = False):
 
         self.mode = mode
 
+        if isinstance(path, PathLike):
+            path = str(path)
+
         self.c_eventlog = _lcm.EventLog (path, mode)
         self.f = None