Lower level causes should be printed on error

[sgryjp]

Would you consider to let csvlens print lower level causes on exiting with an error?

As of v0.5.0, csvlens does not print lower level causes stored in an anyhow::Error instance on error exit. This means that the error message is not very helpful as the root cause is not reported to users. For example, trying to open a non-existent file and trying to open an existing but not UTF-8 encoded file emits completely same message:

$ echo "亜" | iconv -f utf-8 -t cp932 > cp932.csv
$ csvlens cp932.csv
Failed to open file: cp932.csv
$ csvlens no-such-file.csv
Failed to open file: no-such-file.csv

Since an anyhow::Error instance contains lower level causes and provides some ways to extract them, using one of them should solve the situation.

[YS-L]

Hi @sgryjp, yes that makes a lot of sense. Thanks for the suggestion!