Handle pathlib.Path in write_image

Closes plotly#2753

Author: Ben Mares (m2-jupyter)

Diff for: packages/python/plotly/plotly/io/_kaleido.py

@@ -156,7 +156,7 @@ def write_image(
 
     file: str or writeable
         A string representing a local file path or a writeable object
-        (e.g. an open file descriptor)
+        (e.g. a pathlib.Path object or an open file descriptor)
 
     format: str or None
         The desired image format. One of
@@ -258,7 +258,29 @@ def write_image(
         with open(file, "wb") as f:
             f.write(img_data)
     else:
-        file.write(img_data)
+        # Handle a pathlib.Path object
+        # ----------------------------
+        try:
+            file.write_bytes(img_data)
+            return
+        except AttributeError:
+            pass
+        # Handle an open file descriptor
+        # ------------------------------
+        try:
+            file.write(img_data)
+            return
+        except AttributeError:
+            pass
+        # Handlers failed
+        # ---------------
+        raise ValueError(
+            """
+The 'file' argument '{file}' is not a string, pathlib.Path object, or file descriptor.
+""".format(
+                file=file
+            )
+        )
 
 
 def full_figure_for_development(fig, warn=True, as_dict=False):