Refactor init for Excel readers to _BaseExcelReader

[tdamsma]

Pre-cursor for #25092. To support multiple excel readers the init function is moved to _BaseExcelReader. The function is made a bit more general to be able to support multiple excel readers.

• tests passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[jreback]

looks good. ping when ready. cc @WillAyd

[WillAyd]

I see this wasn't carried over - is it no longer valid?

[tdamsma]

This is now dealt with by wrapping url responses in BytesIO(urlopen(filepath_or_buffer).read()). So now all items with "read" can also support seek(0)

[tdamsma]

@jreback, @WillAyd, I don't understand the test failing tests, but other than that I think it's ready

[WillAyd]

@tdamsma restarted all of them. Not sure what is wrong with the checks_and_doc job off the top of my head but looks like this PR introduced some regressions with handling of S3 excel files as shown in the Travis failures.

If you could take a look would be great

[codecov]

Codecov Report

Merging #26233 into master will decrease coverage by 0.01%.
The diff coverage is 90.32%.

@@            Coverage Diff             @@
##           master   #26233      +/-   ##
==========================================
- Coverage   91.97%   91.96%   -0.02%     
==========================================
  Files         175      175              
  Lines       52368    52376       +8     
==========================================
+ Hits        48164    48166       +2     
- Misses       4204     4210       +6

Flag	Coverage Δ
#multiple	90.51% <90.32%> (-0.01%)	⬇️
#single	40.69% <29.03%> (-0.15%)	⬇️

Impacted Files	Coverage Δ
pandas/io/excel/_xlrd.py	94.54% <100%> (+0.6%)	⬆️
pandas/io/excel/_base.py	92.13% <86.36%> (-0.72%)	⬇️
pandas/io/gbq.py	78.94% <0%> (-10.53%)	⬇️
pandas/core/frame.py	96.9% <0%> (-0.12%)	⬇️

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[codecov]

Codecov Report

Merging #26233 into master will decrease coverage by 68.95%.
The diff coverage is 31.25%.

@@             Coverage Diff             @@
##           master   #26233       +/-   ##
===========================================
- Coverage   91.97%   23.01%   -68.96%     
===========================================
  Files         175      175               
  Lines       52368    52377        +9     
===========================================
- Hits        48164    12055    -36109     
- Misses       4204    40322    +36118

Flag	Coverage Δ
#multiple	?
#single	23.01% <31.25%> (-17.83%)	⬇️

Impacted Files	Coverage Δ
pandas/io/excel/_xlrd.py	23.21% <30%> (-70.73%)	⬇️
pandas/io/excel/_base.py	27.94% <31.81%> (-64.91%)	⬇️
pandas/io/formats/latex.py	0% <0%> (-100%)	⬇️
pandas/io/sas/sas_constants.py	0% <0%> (-100%)	⬇️
pandas/core/groupby/categorical.py	0% <0%> (-100%)	⬇️
pandas/tseries/plotting.py	0% <0%> (-100%)	⬇️
pandas/tseries/converter.py	0% <0%> (-100%)	⬇️
pandas/io/formats/html.py	0% <0%> (-99.37%)	⬇️
pandas/core/apply.py	0% <0%> (-98.62%)	⬇️
pandas/io/formats/csvs.py	0% <0%> (-98.2%)	⬇️
... and 140 more

---

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[jreback]

lgtm. @WillAyd

[tdamsma]

@WillAyd, I addressed the regression. Also I accidentally committed (and reverted) a setting to limit the test scope, that explains the codecov report.

[WillAyd]

Nice job @tdamsma - looking forward to the follow ups!

[tdamsma]

Great, thanks for the reviews