"Validate sample data" task—and model tests—fail on a SyntaxError in validation.py

[emilyanndavis]

After a fresh clone of the sample data (i.e., after deleting the data/invest-sample-data folder), make validate_sampledata is crashing on the following error:

File "invest/src/natcap/invest/validation.py", line 645
   patterns.append(column.replace('(', '\(').replace(')', '\)'))
                                       ^^^^
SyntaxError: invalid escape sequence '\('

[emilyanndavis]

This is also affecting unit test suites that rely on validation.py (in other words, probably all of the model tests).