guildai: Error when View in TensorBoard clicked in Guild View

Copied from #5:

`/anaconda3/lib/python3.6/site-packages/h5py/init.py:36: FutureWarning: Conversion of the second argument of issubdtype from float to np.floating is deprecated. In future, it will be treated as np.float64 == np.dtype(float).type.
from ._conv import register_converters as _register_converters
Traceback (most recent call last):
File "/anaconda3/lib/python3.6/site-packages/guild/commands/tensorboard_impl.py", line 106, in _load_guild_tensorboard_module
from guild import tensorboard
File "/anaconda3/lib/python3.6/site-packages/guild/tensorboard.py", line 51, in 
from tensorboard.plugins.audio import audio_plugin
File "/Users/bdorsey/.local/lib/python3.6/site-packages/tensorboard/plugins/audio/audio_plugin.py", line 27, in 
from tensorboard import plugin_util
File "/Users/bdorsey/.local/lib/python3.6/site-packages/tensorboard/plugin_util.py", line 24, in 
import markdown
ModuleNotFoundError: No module named 'markdown'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/anaconda3/lib/python3.6/site-packages/guild/scripts/guild", line 30, in 
main()
File "/anaconda3/lib/python3.6/site-packages/guild/scripts/guild", line 23, in main
guild.main_bootstrap.main()
File "/anaconda3/lib/python3.6/site-packages/guild/main_bootstrap.py", line 44, in main
guild.main.main()
File "/anaconda3/lib/python3.6/site-packages/guild/main.py", line 30, in main
_main()
File "/anaconda3/lib/python3.6/site-packages/guild/main.py", line 36, in _main
guild.commands.main.main(standalone_mode=False)
File "/anaconda3/lib/python3.6/site-packages/guild/external/click/core.py", line 731, in call
return self.main(*args, **kwargs)
File "/anaconda3/lib/python3.6/site-packages/guild/external/click/core.py", line 706, in main
rv = self.invoke(ctx)
File "/anaconda3/lib/python3.6/site-packages/guild/external/click/core.py", line 1080, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "/anaconda3/lib/python3.6/site-packages/guild/external/click/core.py", line 907, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/anaconda3/lib/python3.6/site-packages/guild/external/click/core.py", line 544, in invoke
return callback(args, **kwargs)
File "/anaconda3/lib/python3.6/site-packages/guild/click_util.py", line 140, in fn
return fn0((args + (Args(kw),)))
File "/anaconda3/lib/python3.6/site-packages/guild/commands/tensorboard.py", line 74, in tensorboard
tensorboard_impl.main(args)
File "/anaconda3/lib/python3.6/site-packages/guild/commands/tensorboard_impl.py", line 86, in main
tensorboard = _load_guild_tensorboard_module()
File "/anaconda3/lib/python3.6/site-packages/guild/commands/tensorboard_impl.py", line 108, in _load_guild_tensorboard_module
_handle_tensorboard_import_error(e)
File "/anaconda3/lib/python3.6/site-packages/guild/commands/tensorboard_impl.py", line 113, in _handle_tensorboard_import_error
if e.message == 'No module named tensorflow':
AttributeError: 'ModuleNotFoundError' object has no attribute 'message'`