tests: fix ObsPy again

[reidpr]

ObsPy has started failing again:

 ✗ obspy/hello
   (in test file /home/reidpr/charliecloud/examples/obspy/test.bats, line 16)
     `ch-run -b "$BATS_TMPDIR":/mnt "$ch_img" -- /hello.py /mnt/obspy.png' failed
   Traceback (most recent call last):
     File "/hello.py", line 13, in <module>
       from obspy import read
     File "/usr/local/lib/python3.9/site-packages/obspy/__init__.py", line 39, in <module>
       from obspy.core.utcdatetime import UTCDateTime  # NOQA
     File "/usr/local/lib/python3.9/site-packages/obspy/core/__init__.py", line 124, in <module>
       from obspy.core.utcdatetime import UTCDateTime  # NOQA
     File "/usr/local/lib/python3.9/site-packages/obspy/core/utcdatetime.py", line 27, in <module>
       from obspy.core.util.deprecation_helpers import ObsPyDeprecationWarning
     File "/usr/local/lib/python3.9/site-packages/obspy/core/util/__init__.py", line 27, in <module>
       from obspy.core.util.base import (ALL_MODULES, DEFAULT_MODULES,
     File "/usr/local/lib/python3.9/site-packages/obspy/core/util/base.py", line 36, in <module>
       from obspy.core.util.misc import to_int_or_zero, buffered_load_entry_point
     File "/usr/local/lib/python3.9/site-packages/obspy/core/util/misc.py", line 214, in <module>
       loadtxt(np.array([0]), ndmin=1)
     File "/usr/local/lib/python3.9/site-packages/numpy/lib/npyio.py", line 1086, in loadtxt
       ncols = len(usecols or split_line(first_line))
     File "/usr/local/lib/python3.9/site-packages/numpy/lib/npyio.py", line 977, in split_line
       line = line.split(comment, 1)[0]
   AttributeError: 'numpy.int64' object has no attribute 'split'
 ✗ obspy/hello PNG
   (from function `pict_assert_equal' in file common.bash, line 179,
    in test file /home/reidpr/charliecloud/examples/obspy/test.bats, line 21)
     `pict_assert_equal "$CHTEST_EXAMPLES_DIR"/obspy/obspy.png \' failed
   reference:   /home/reidpr/charliecloud/examples/obspy/obspy.png
   sample:      /tmp/ch-test.tmp.reidpr/bats.tmp/obspy.png
   diff image:  /tmp/ch-test.tmp.reidpr/bats.tmp/obspy.diff.png
   diff count:  compare-im6.q16: unable to open image `/tmp/ch-test.tmp.reidpr/bats.tmp/obspy.png': No such file or directory @ error/blob.c/OpenBlob/2924. pixels, max 0
   /home/reidpr/charliecloud/test/common.bash: line 179: compare-im6.q16: unable to open image `/tmp/ch-test.tmp.reidpr/bats.tmp/obspy.png': No such file or directory @ error/blob.c/OpenBlob/2924.: syntax error: invalid arithmetic operator (error token is ".q16: unable to open image `/tmp/ch-test.tmp.reidpr/bats.tmp/obspy.png': No such file or directory @ error/blob.c/OpenBlob/2924.")

Possible resources:

• https://discourse.obspy.org/t/problem-running-obspy-in-docker-container/1364
• the problem of QuakeLabeler used in the Ubuntu maihao14/QuakeLabeler#5

I'd really like someone with ObsPy expertise to maintain this example image.