What is the best way to handle ImportError - Raise error or import chain?

Question

Question

When you encounter ImportError in python, should I directly raise the error and ask the user to install it or use the import chain?

Description

I came across this question when I tried to use the lxml package to parse an XML file in python.
The official documentation says:

If your code uses the ElementTree API and does not rely on any functionality specific to lxml.etree, you can also use (any part) the following import chain as a return to the original ElementTree:

try:
    from lxml import etree
    print("running with lxml.etree")
except ImportError:
    try:
        import xml.etree.cElementTree as etree
        print("running with cElementTree on Python 2.5+")
    except ImportError:
        ...

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Answer 1

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try:
    import super_fast_widget as widget
except ImportError:
    try:
        import fast_widget as widget
    except ImportError:
        import slow_widget as widget

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Django:

# Use the C (faster) implementation if possible
try:
    from yaml import CSafeLoader as SafeLoader
    from yaml import CSafeDumper as SafeDumper
except ImportError:
    from yaml import SafeLoader, SafeDumper

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Answer 2

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Error increase

Traceback (most recent call last):
  File "core.py", line 1, in <module>
ImportError: <error description>

Import Chains

i Importing "lxml.etree"
x Error Importing "lxml.etree"
i Importing "xml.etree.cElementTree" on Python 2.5+
x Error Importing "xml.etree.cElementTree" on Python 2.5+
i Please Install "lxml.etree" or "xml.etree.xElementTree" on Python 2.5+
i Exit with code 1