Kaleido does not raise exception when `plotlyjs` path argument is a nonexistent file

[emilykl]

Situation

• A nonexistent filepath is passed as the plotlyjs argument when creating a Kaleido instance. The plotlyjs argument is supposed to be either a local path or a URL which points to the Plotly.js script.

Expected behavior

Kaleido() raises an exception if the plotlyjs path does not point to an actual file

Actual behavior

Kaleido is instantiated successfully. Later, when trying to generate an image, the generation fails with a JS Plotly is not defined error:

 kaleido._kaleido_tab.JavascriptError: {'result': {'type': 'object', 'subtype': 'error', 'className': 'ReferenceError', 'description': 'ReferenceError: Plotly is not defined\n    at Object.render [as plotly] (file:///Users/ekl/code/plotly.py/venv/plotly.py/lib/python3.12/site-packages/kaleido/vendor/kaleido_scopes.js:3021:18)\n    at <anonymous>:1:48', 'objectId': '7443417724967587290.1.1'}, 'exceptionDetails': {'exceptionId': 1, 'text': 'Uncaught', 'lineNumber': 3020, 'columnNumber': 17, 'scriptId': '7', 'stackTrace': {'callFrames': [{'functionName': 'render', 'scriptId': '7', 'url': 'file:///Users/ekl/code/plotly.py/venv/plotly.py/lib/python3.12/site-packages/kaleido/vendor/kaleido_scopes.js', 'lineNumber': 3020, 'columnNumber': 17}, {'functionName': '', 'scriptId': '11', 'url': '', 'lineNumber': 0, 'columnNumber': 47}]}, 'exception': {'type': 'object', 'subtype': 'error', 'className': 'ReferenceError', 'description': 'ReferenceError: Plotly is not defined\n    at Object.render [as plotly] (file:///Users/ekl/code/plotly.py/venv/plotly.py/lib/python3.12/site-packages/kaleido/vendor/kaleido_scopes.js:3021:18)\n    at <anonymous>:1:48', 'objectId': '7443417724967587290.1.2'}}}

Code to reproduce:

import asyncio

import kaleido
import plotly.graph_objects as go


asyncio.run(
    kaleido.write_fig(
        go.Figure([go.Bar(x=[1, 2, 3], y=[4, 5, 6])]),
        "bar_chart.png",
        kopts={"plotlyjs": "path/to/file/which/does/not/exist.js"}
    )
)