cool-RR opened a new pull request #7416:
URL: https://github.com/apache/arrow/pull/7416


   I recently went over 
[Matplotlib](https://github.com/matplotlib/matplotlib/pull/16706), 
[Pandas](https://github.com/pandas-dev/pandas/pull/32322) and 
[NumPy](https://github.com/numpy/numpy/pull/15731), fixing a small mistake in 
the way that Python 3's exception chaining is used. If you're interested, I can 
do it here too. I've done it on just one file right now. 
   
   The mistake is this: In some parts of the code, an exception is being caught 
and replaced with a more user-friendly error. In these cases the syntax `raise 
new_error from old_error` needs to be used.
   
   Python 3's exception chaining means it shows not only the traceback of the 
current exception, but that of the original exception (and possibly more.) This 
is regardless of `raise from`. The usage of `raise from` tells Python to put a 
more accurate message between the tracebacks. Instead of this: 
   
       During handling of the above exception, another exception occurred:
   
   You'll get this: 
   
       The above exception was the direct cause of the following exception:
   
   The first is inaccurate, because it signifies a bug in the 
exception-handling code itself, which is a separate situation than wrapping an 
exception.
   
   Let me know what you think! 


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