Test random indicators and intercept JSONDecodeError

[mwouts]

As suggested by @bcipolli at #7.

With this update, we get the following output:

ENF.CONT.COEN.CSMG: OK
IN.IS.RRS.PASG.KM.SUB: OK
UIS.NAR.2: OK
FB.FCP.INST.CB.PD.SW: OK
IP.TMK.RSCT: OK
IT.NET.BNDW.PC: OK
per_lm_pa.adq_q2_preT_tot: OK
NV.IND.MANF.KD.87: ERROR:
The indicator was not found. It may have been deleted or archived.
url=http://api.worldbank.org/v2/country/all/indicator/NV.IND.MANF.KD.87
params={'mrv': 1, 'format': 'jsonstat', 'per_page': 20000}
SABER.WORK.GOAL2: OK
IN.EC.POP.RURL.PCT: OK
SE.SEC.PROG.MA.ZS: OK
SN.ITK.VITA.Q5.ZS: OK

for this code snippet:

import sys
import random
import world_bank_data as wb

all_indics = wb.get_indicators()

random.seed(2019)
for indicator in random.sample(all_indics.index.tolist(), 12):
    sys.stdout.write(indicator + ':')
    try:
        value = wb.get_series(indicator, mrv=1)
        sys.stdout.write(' OK\n')
    except ValueError as err:
        sys.stdout.write(' ERROR:\n')
        sys.stdout.write(str(err) + '\n')

[codecov-io]

Codecov Report

Merging #11 into master will increase coverage by <.01%.
The diff coverage is 96%.

@@            Coverage Diff             @@
##           master      #11      +/-   ##
==========================================
+ Coverage   95.91%   95.92%   +<.01%     
==========================================
  Files          16       16              
  Lines         392      417      +25     
==========================================
+ Hits          376      400      +24     
- Misses         16       17       +1

Impacted Files	Coverage Δ
tests/test_indicator.py	96.42% <100%> (+0.84%)	⬆️
world_bank_data/request.py	94.79% <88.88%> (-0.62%)	⬇️

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