Fix "no such directory error" on startup

[da-h]

Description

This PR solves the "no such directory error" when starting visdom with an -env_path that does not exist. For new users this is even the case for just calling visdom without any arguments.

Background:
In trying to solve one issue, I have to admit, I created another one in PR #839.
Reason for this shortcoming is probably that the function ensure_dir_exists has previously created the directory for the parent of the given path, i.e. expecting a proper file-path, but, it has been used in two variants in the code:

1. first for layouts (in the function load_layouts), where it has been called on a specific layout.json-file
2. for arbitrary env_paths, where the function did only work when the path given by the user would have ended with a path-delimiter (/). (what i wanted to solve in Fix Relative Env Path Errors #839).

This PR solves this issue by

1. letting the function work specifically on directories, as the name suggests. by using os.path.abspath the function would also normalize any trailing path-delimiter (/)
2. ensuring that all uses (only two in the code-base) of that function call it with a directories
3. on the way I say that the function has been called in load_layouts even if the path already existed, thus I (re)moved ensure_dir_exists there
4. i have also added the working directory to the logger-output so that users know where their data is stored

Motivation and Context

See issues #875 and #874 for details. (This issue should solve both of these.)

How Has This Been Tested?

The following variants are working with this PR in place:

• Startup:
  • visdom (creates $HOME/.visdom if it does not exist)
  • visdom -env_path /tmp/doesnotexist (creates directory)
  • visdom -env_path /tmp/doesnotexist/ (creates directory also with a trailing /)
  • visdom -env_path . (enabled by the change of vis.svg(svg_file=xxx) not working #613 )
• Layout Saving: (as this has been changed in the PR as well)
  • start visdom → select any env and any view → open "manage views" window (the folder on the right of the menu bar) → check that "fork" and "delete" work as expected

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactor or cleanup (changes to existing code for improved readability or performance)

Checklist:

• I adapted the version number under py/visdom/VERSION according to Semantic Versioning
  Minor version increase to 0.2.3.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

Note

The checks will probably fail, till #880 and #879 is merged.

[da-h]

Rebased onto master.