Bug#1101527: pandas fails its autopkgtests

[Rebecca N. Palmer]

Control: tags -1 pending

The part you refer to isn't the autopkgtest failure - pandas' pymysql 
and psycopg2 tests are known not to work in our test environments, so 
the main autopkgtest doesn't install these.  To monitor this, an extra 
'ignoredtests' does install them but ignores the resulting 
failures/crashes, so the logs are expected to contain such error 
messages but these are not actually autopkgtest failures.

The actual test failures are test_boxplot*, and appear to be caused by 
matplotlib adding a new warning (the pandas tests default to failing on 
warnings).

The version I have pushed to Salsa (and intend to upload if it passes 
CI) adds this warning to the pandas tests' ignore list.