Issue on page /modules/m4/4.1-WhatAndWhy.html

[prestevez]

The first and last code blocks throw an error. I think it is due to a missing graphviz package.

I recloned the repo and reinstalled the poetry dependencies, but the error persists.

Error message (it is the same for both code blocks):

---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
~/.cache/pypoetry/virtualenvs/rds-course--MwjGM7k-py3.8/lib/python3.8/site-packages/graphviz/backend/execute.py in run_check(cmd, input_lines, encoding, quiet, **kwargs)
     78                 kwargs['stdout'] = kwargs['stderr'] = subprocess.PIPE
---> 79             proc = _run_input_lines(cmd, input_lines, kwargs=kwargs)
     80         else:

~/.cache/pypoetry/virtualenvs/rds-course--MwjGM7k-py3.8/lib/python3.8/site-packages/graphviz/backend/execute.py in _run_input_lines(cmd, input_lines, kwargs)
     98 def _run_input_lines(cmd, input_lines, *, kwargs):
---> 99     popen = subprocess.Popen(cmd, stdin=subprocess.PIPE, **kwargs)
    100 

/usr/lib/python3.8/subprocess.py in __init__(self, args, bufsize, executable, stdin, stdout, stderr, preexec_fn, close_fds, shell, cwd, env, universal_newlines, startupinfo, creationflags, restore_signals, start_new_session, pass_fds, encoding, errors, text)
    857 
--> 858             self._execute_child(args, executable, preexec_fn, close_fds,
    859                                 pass_fds, cwd, env,

/usr/lib/python3.8/subprocess.py in _execute_child(self, args, executable, preexec_fn, close_fds, pass_fds, cwd, env, startupinfo, creationflags, shell, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite, restore_signals, start_new_session)
   1703                         err_msg = os.strerror(errno_num)
-> 1704                     raise child_exception_type(errno_num, err_msg, err_filename)
   1705                 raise child_exception_type(err_msg)

FileNotFoundError: [Errno 2] No such file or directory: PosixPath('dot')

The above exception was the direct cause of the following exception:
...
---> 84             raise ExecutableNotFound(cmd) from e
     85         raise
     86 

ExecutableNotFound: failed to execute PosixPath('dot'), make sure the Graphviz executables are on your systems' PATH
<graphviz.graphs.Digraph at 0x7f7ea8f34490>

[craddm]

This is a missing system dependency - you beat me to reporting this one. On Mac, brew install graphviz will do it. Otherwise, check the Graphviz website. We'll work out how to fix this for the future.

[jack89roberts]

Could solve it by using a conda environment I think (or adding it to the setup instructions, but as per #112 poetry isn't the right choice for this course imo).