Fix superficial build test errors

6 jobs for master in 3855 minutes and 21 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed job_clang_amd64 #1832
amd64

15:09:22

failed job_clang_amd64_nosh #1836
amd64

14:26:49

failed job_clang_py2_amd64 #1834
amd64

02:00:40

passed job_gcc_amd64 #1831
amd64

16:04:46

failed job_gcc_amd64_nosh #1835
amd64

15:03:30

failed job_gcc_py2_amd64 #1833
amd64

01:30:12

 
Name Stage Failure
failed
job_gcc_py2_amd64 Test There is an unknown failure, please try again

Document: centrality
--------------------

Encoding error:
'ascii' codec can't decode byte 0xcb in position 401: ordinal not in range(128)
The full traceback has been saved in /tmp/sphinx-err-bBcTiM.log, if you want to report the issue to the developers.

ERROR: Build failed: exit status 1
failed
job_clang_py2_amd64 Test There is an unknown failure, please try again

Document: centrality
--------------------

Encoding error:
'ascii' codec can't decode byte 0xb3 in position 402: ordinal not in range(128)
The full traceback has been saved in /tmp/sphinx-err-TQaKTn.log, if you want to report the issue to the developers.

ERROR: Build failed: exit status 1
failed
job_gcc_amd64_nosh Test There is an unknown failure, please try again
  max_open_warning, RuntimeWarning)
<string>:10: VisibleDeprecationWarning: using a non-integer number instead of an integer will result in an error in the future
/usr/lib/python3.5/site-packages/matplotlib/pyplot.py:516: RuntimeWarning: More than 20 figures have been opened. Figures created through the pyplot interface (`matplotlib.pyplot.figure`) are retained until explicitly closed and may consume too much memory. (To control this warning, see the rcParam `figure.max_open_warning`).
max_open_warning, RuntimeWarning)
<string>:17: RuntimeWarning: divide by zero encountered in log
/usr/lib/python3.5/site-packages/matplotlib/pyplot.py:516: RuntimeWarning: More than 20 figures have been opened. Figures created through the pyplot interface (`matplotlib.pyplot.figure`) are retained until explicitly closed and may consume too much memory. (To control this warning, see the rcParam `figure.max_open_warning`).
max_open_warning, RuntimeWarning)

ERROR: Build failed: exit status 1
failed
job_clang_amd64_nosh Test There is an unknown failure, please try again
  warnings.warn("tight_layout : falling back to Agg renderer")
/usr/lib/python3.5/site-packages/matplotlib/pyplot.py:516: RuntimeWarning: More than 20 figures have been opened. Figures created through the pyplot interface (`matplotlib.pyplot.figure`) are retained until explicitly closed and may consume too much memory. (To control this warning, see the rcParam `figure.max_open_warning`).
max_open_warning, RuntimeWarning)
/usr/lib/python3.5/site-packages/matplotlib/tight_layout.py:222: UserWarning: tight_layout : falling back to Agg renderer
warnings.warn("tight_layout : falling back to Agg renderer")
/usr/lib/python3.5/site-packages/matplotlib/pyplot.py:516: RuntimeWarning: More than 20 figures have been opened. Figures created through the pyplot interface (`matplotlib.pyplot.figure`) are retained until explicitly closed and may consume too much memory. (To control this warning, see the rcParam `figure.max_open_warning`).
max_open_warning, RuntimeWarning)

ERROR: Build failed: exit status 1