tox failures during `make test-all`

[cicorias]

during a run of make test-all tests fails. see pyenv/pyenv-virtualenv#206 and tox-dev/tox-pyenv#4

flake8 runtests: commands[0] | flake8 cli
__________________________________________________________________________________________________________ summary __________________________________________________________________________________________________________
  py35: commands succeeded
ERROR:   py36: Error creating virtualenv. Note that some special characters (e.g. ':' and unicode symbols) in paths are not supported by virtualenv. Error details: InvocationError("Failed to get version_info for python3.6: pyenv: python3.6: command not found\n\nThe `python3.6' command exists in these Python versions:\n  3.6.8\n  3.6.8/envs/py36\n  3.6.8/envs/py368\n  py36\n  py368\n\n", None)
  py37: commands succeeded
  flake8: commands succeeded
(py35) cicorias@cicoria-msi:/c/g/cse/tiem/agogosml/agogosml_cli$

more verbose

GLOB finish: packaging after 0.24 seconds
copying new sdistfile to '/root/.tox/distshare/example-pkg-your-username-0.0.1.zip'
package .tmp/package/1/example-pkg-your-username-0.0.1.zip links to dist/example-pkg-your-username-0.0.1.zip (/app/.tox)
py35 start: getenv /app/.tox/py35
py35 cannot reuse: no previous config /app/.tox/py35/.tox-config1
py35 create: /app/.tox/py35
ERROR: Error creating virtualenv. Note that some special characters (e.g. ':' and unicode symbols) in paths are not supported by virtualenv. Error details: InvocationError("Failed to get version_info for python3.5: pyenv: python3.5: command not found\n\nThe `python3.5' command exists in these Python versions:\n  3.5.6\n\n", None)
py35 finish: getenv after 0.05 seconds
py36 start: getenv /app/.tox/py36
py36 cannot reuse: no previous config /app/.tox/py36/.tox-config1
py36 create: /app/.tox/py36
ERROR: Error creating virtualenv. Note that some special characters (e.g. ':' and unicode symbols) in paths are not supported by virtualenv. Error details: InvocationError("Failed to get version_info for python3.6: pyenv: python3.6: command not found\n\nThe `python3.6' command exists in these Python versions:\n  3.6.8\n\n", None)
py36 finish: getenv after 0.05 seconds
___________________________________________________________________________________________________________________ summary ___________________________________________________________________________________________________________________ERROR:   py35: Error creating virtualenv. Note that some special characters (e.g. ':' and unicode symbols) in paths are not supported by virtualenv. Error details: InvocationError("Failed to get version_info for python3.5: pyenv: python3.5: command not found\n\nThe `python3.5' command exists in these Python versions:\n  3.5.6\n\n", None)
ERROR:   py36: Error creating virtualenv. Note that some special characters (e.g. ':' and unicode symbols) in paths are not supported by virtualenv. Error details: InvocationError("Failed to get version_info for python3.6: pyenv: python3.6: command not found\n\nThe `python3.6' command exists in these Python versions:\n  3.6.8\n\n", None)
cleanup /app/.tox/.tmp/package/1/example-pkg-your-username-0.0.1.zip