Pyppeteer / Puppeteer NetworkError：执行上下文被破坏，很可能是因为导航

Question

我正在使用 puppeteer 进行一些轻量的爬行 ~2K 页面。但我不断看到这个错误再次出现

  File "/env/local/lib/python3.7/site-packages/pyppeteer/execution_context.py", line 106, in evaluateHandle
    'userGesture': True,
pyppeteer.errors.NetworkError: Protocol error (Runtime.callFunctionOn): Cannot find context with specified id

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
...
  File "/user_code/main.py", line 434, in main_program
    crawl_data = asyncio.get_event_loop().run_until_complete(crawl(browser, url))
  File "/opt/python3.7/lib/python3.7/asyncio/base_events.py", line 573, in run_until_complete
    return future.result()
  File "/user_code/main.py", line 394, in crawl
    title = await page.title()
  File "/env/local/lib/python3.7/site-packages/pyppeteer/page.py", line 1437, in title
    return await frame.title()
  File "/env/local/lib/python3.7/site-packages/pyppeteer/frame_manager.py", line 752, in title
    return await self.evaluate('() => document.title')
  File "/env/local/lib/python3.7/site-packages/pyppeteer/frame_manager.py", line 295, in evaluate
    pageFunction, *args, force_expr=force_expr)
  File "/env/local/lib/python3.7/site-packages/pyppeteer/execution_context.py", line 55, in evaluate
    pageFunction, *args, force_expr=force_expr)
  File "/env/local/lib/python3.7/site-packages/pyppeteer/execution_context.py", line 109, in evaluateHandle
    _rewriteError(e)
  File "/env/local/lib/python3.7/site-packages/pyppeteer/execution_context.py", line 238, in _rewriteError
    raise type(error)(msg)
pyppeteer.errors.NetworkError: Execution context was destroyed, most likely because of a navigation.
"  

我不明白它是如何触发与相关的错误frame.title()因为在我的代码中，它只查找实际的页面标题而不是在其框架内。

此外，它在导航到任何框架内容之前调用页面标题：

  File "/env/local/lib/python3.7/site-packages/pyppeteer/execution_context.py", line 106, in evaluateHandle
    'userGesture': True,
pyppeteer.errors.NetworkError: Protocol error (Runtime.callFunctionOn): Cannot find context with specified id

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
...
  File "/user_code/main.py", line 434, in main_program
    crawl_data = asyncio.get_event_loop().run_until_complete(crawl(browser, url))
  File "/opt/python3.7/lib/python3.7/asyncio/base_events.py", line 573, in run_until_complete
    return future.result()
  File "/user_code/main.py", line 394, in crawl
    title = await page.title()
  File "/env/local/lib/python3.7/site-packages/pyppeteer/page.py", line 1437, in title
    return await frame.title()
  File "/env/local/lib/python3.7/site-packages/pyppeteer/frame_manager.py", line 752, in title
    return await self.evaluate('() => document.title')
  File "/env/local/lib/python3.7/site-packages/pyppeteer/frame_manager.py", line 295, in evaluate
    pageFunction, *args, force_expr=force_expr)
  File "/env/local/lib/python3.7/site-packages/pyppeteer/execution_context.py", line 55, in evaluate
    pageFunction, *args, force_expr=force_expr)
  File "/env/local/lib/python3.7/site-packages/pyppeteer/execution_context.py", line 109, in evaluateHandle
    _rewriteError(e)
  File "/env/local/lib/python3.7/site-packages/pyppeteer/execution_context.py", line 238, in _rewriteError
    raise type(error)(msg)
pyppeteer.errors.NetworkError: Execution context was destroyed, most likely because of a navigation.
"  

重复出现此错误的可能原因是什么？