fix: Add default request headers to Kaleido calls

CHANGELOG.md

@@ -11,6 +11,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Fix issue where user-specified `color_continuous_scale` was ignored when template had `autocolorscale=True` [[#5439](https://github.com/plotly/plotly.py/pull/5439)], with thanks to @antonymilne for the contribution!
 - Use presence of `COLAB_NOTEBOOK_ID` env var to enable Colab renderer instead of testing import of `google.colab` [[#5473](https://github.com/plotly/plotly.py/pull/5473)], with thanks to @kevineger for the contribution!
 - Update tests to be compatible with numpy 2.4 [[#5522](https://github.com/plotly/plotly.py/pull/5522)], with thanks to @thunze for the contribution!
+- Add default headers to be passed in to Kaleido v1.3.0 to avoid blocked Open Street Map tiles [#5588](https://github.com/plotly/plotly.py/pull/5588)]
 
 ### Updated
 - The `__eq__` method for  `graph_objects` classes now returns `NotImplemented` to give the other operand an opportunity to handle the comparison [[#5547](https://github.com/plotly/plotly.py/pull/5547)], with thanks to @RazerM for the contribution!

plotly/io/_defaults.py

@@ -14,6 +14,9 @@ def __init__(self):
         self.mathjax = None
         self.topojson = None
         self.plotlyjs = None
+        # This header is necessary to comply with Open Street Map tile policy:
+        # https://openstreetmap.github.io/owg-website/policies/tiles/#31-identification
+        self.headers = {"X-Requested-With": "plotly.py"}
 
 
 defaults = _Defaults()

plotly/io/_kaleido.py

@@ -375,6 +375,8 @@ def to_image(
                 kopts["plotlyjs"] = defaults.plotlyjs
             if defaults.mathjax:
                 kopts["mathjax"] = defaults.mathjax
+            if defaults.headers:
+                kopts["headers"] = defaults.headers
 
             width = (
                 width
@@ -712,6 +714,8 @@ def write_images(
             kopts["plotlyjs"] = defaults.plotlyjs
         if defaults.mathjax:
             kopts["mathjax"] = defaults.mathjax
+        if defaults.headers:
+            kopts["headers"] = defaults.headers
         kaleido.write_fig_from_object_sync(
             kaleido_specs,
             kopts=kopts,