How to get the versions of dependecies

[Cecil Westerhof]

If I update prompt-toolkit, I get:
    ipython 6.4.0 has requirement prompt-toolkit<2.0.0,>=1.0.15, but you'll have prompt-toolkit 2.0.3 which is incompatible.

So I should not. At least not at the moment. But how do I get to know
which versions of a package are needed?

When Using:
    pip3 -vvv show ipython

I just get:
    Name: ipython
    Version: 6.4.0
    Summary: IPython: Productive Interactive Computing
    Home-page: https://ipython.org
    Author: The IPython Development Team
    Author-email: ipython-dev at python.org
    License: BSD
    Location: /usr/local/lib/python3.5/dist-packages
    Requires: traitlets, decorator, pickleshare, backcall, prompt-toolkit, pexpect, jedi, simplegeneric, setuptools, pygments
    Required-by: 
    Metadata-Version: 2.0
    Installer: pip
    Classifiers:
      Framework :: IPython
      Intended Audience :: Developers
      Intended Audience :: Science/Research
      License :: OSI Approved :: BSD License
      Programming Language :: Python
      Programming Language :: Python :: 3
      Programming Language :: Python :: 3 :: Only
      Topic :: System :: Shells
    Entry-points:
      [console_scripts]
      iptest = IPython.testing.iptestcontroller:main
      iptest3 = IPython.testing.iptestcontroller:main
      ipython = IPython:start_ipython
      ipython3 = IPython:start_ipython
      [pygments.lexers]
      ipython = IPython.lib.lexers:IPythonLexer
      ipython3 = IPython.lib.lexers:IPython3Lexer
      ipythonconsole = IPython.lib.lexers:IPythonConsoleLexer

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof