strip added to excel extractor breaks extraction ()

[aleksandra-kim]

Original report by Pascal Lesage (Bitbucket: MPa, ).

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Strip added to extractor in commit 3390d0f results in AttributeError when importing Excel:

c:\mypy\code\brightway2-io\bw2io\extractors\excel.py in <lambda>(x)
     17     def extract_sheet(cls, wb, name, strip=True):
     18         ws = wb.sheet_by_name(name)
---> 19         _ = lambda x: x.strip() if strip else x
     20         return [[_(ws.cell(row, col).value) for col in range(ws.ncols)] for row in range(ws.nrows)]
     21 
AttributeError: 'float' object has no attribute 'strip'

Tested on file "sample_activities_with_variables.xlsx"

[aleksandra-kim]

Original comment by Chris Mutel (Bitbucket: cmutel, GitHub: cmutel).

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0.5.12. Fixes #42