Why doesn't virtualenv contain a module for pip when it creates a python environment for me?

Question

I might have multiple problems here but they both deal with virtualenv and python3 (3.6.13).

Problem 1: I had installed virtualenv==20.14.1. However, it's complaining that there's a version conflict for some reason.

$ python3 -V
Python 3.6.13
$ virtualenv -h
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/dist-packages/pkg_resources/__init__.py", line 573, in _build_master
    ws.require(__requires__)
  File "/usr/local/lib/python3.6/dist-packages/pkg_resources/__init__.py", line 891, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/usr/local/lib/python3.6/dist-packages/pkg_resources/__init__.py", line 782, in resolve
    raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.VersionConflict: (virtualenv 20.14.1 (/home/mylogin/.local/lib/python3.6/site-packages), Requirement.parse('virtualenv==15.0.1'))
 
During handling of the above exception, another exception occurred:
 
Traceback (most recent call last):
  File "/usr/bin/virtualenv", line 5, in <module>
    from pkg_resources import load_entry_point
  File "/usr/local/lib/python3.6/dist-packages/pkg_resources/__init__.py", line 3266, in <module>
    @_call_aside
  File "/usr/local/lib/python3.6/dist-packages/pkg_resources/__init__.py", line 3241, in _call_aside
    f(*args, **kwargs)
  File "/usr/local/lib/python3.6/dist-packages/pkg_resources/__init__.py", line 3279, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "/usr/local/lib/python3.6/dist-packages/pkg_resources/__init__.py", line 575, in _build_master
    return cls._build_from_requirements(__requires__)
  File "/usr/local/lib/python3.6/dist-packages/pkg_resources/__init__.py", line 588, in _build_from_requirements
    dists = ws.resolve(reqs, Environment())
  File "/usr/local/lib/python3.6/dist-packages/pkg_resources/__init__.py", line 777, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'virtualenv==15.0.1' distribution was not found and is required by the application
$

Problem 2: I downgraded virtualenv to be 15.0.1 like it said it needed but then it complains that there's a missing module called dataclasses. For some reason, my co-workers don't have this problem but we can't figure out what is different between my setup and their setup.

$ virtualenv mydir -p python3.6
Running virtualenv with interpreter /usr/bin/python3.6
Using base prefix '/usr'
New python executable in /tmp/mydir/bin/python3.6
Also creating executable in /tmp/mydir/bin/python
Installing setuptools, pip, wheel...done.
/tmp/mydir$ source bin/activate
(mydir) myhost:/tmp/mydir$ python -V
Python 3.6.13
(mydir) myhost:/tmp/mydir$ python -m pip -V      
Traceback (most recent call last):
  File "/usr/lib/python3.6/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.6/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/tmp/mydir/lib/python3.6/site-packages/pip/__main__.py", line 29, in <module>
    from pip._internal.cli.main import main as _main
  File "/tmp/mydir/lib/python3.6/site-packages/pip/_internal/cli/main.py", line 9, in <module>
    from pip._internal.cli.autocompletion import autocomplete
  File "/tmp/mydir/lib/python3.6/site-packages/pip/_internal/cli/autocompletion.py", line 10, in <module>
    from pip._internal.cli.main_parser import create_main_parser
  File "/tmp/mydir/lib/python3.6/site-packages/pip/_internal/cli/main_parser.py", line 8, in <module>
    from pip._internal.cli import cmdoptions
  File "/tmp/mydir/lib/python3.6/site-packages/pip/_internal/cli/cmdoptions.py", line 23, in <module>
    from pip._internal.cli.parser import ConfigOptionParser
  File "/tmp/mydir/lib/python3.6/site-packages/pip/_internal/cli/parser.py", line 12, in <module>
    from pip._internal.configuration import Configuration, ConfigurationError
  File "/tmp/mydir/lib/python3.6/site-packages/pip/_internal/configuration.py", line 20, in <module>
    from pip._internal.exceptions import (
  File "/tmp/mydir/lib/python3.6/site-packages/pip/_internal/exceptions.py", line 14, in <module>
    from pip._vendor.rich.console import Console, ConsoleOptions, RenderResult
  File "/tmp/mydir/lib/python3.6/site-packages/pip/_vendor/rich/console.py", line 7, in <module>
    from dataclasses import dataclass, field
ModuleNotFoundError: No module named 'dataclasses'

This seems to be a chicken and the egg problem. I would run pip to install this missing module but pip is the program that is complaining about this missing module so I can't install it. Like I said above, none of my co-workers I asked know what the problem is.

For debugging purposes, I installed python 2.7.12 and virtualenv==20.14.1 to see what would happen. Apparently things work fine with python 2.7.

$ pip freeze | grep virtual
DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. pip 21.0 will drop support for Python 2.7 in January 2021. More details about Python 2 support in pip can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support pip 21.0 will remove support for this functionality.
virtualenv==20.14.1
virtualenv-clone==0.5.3
virtualenvwrapper==4.8.4
myhost:/tmp$ virtualenv zzz -p python
Running virtualenv with interpreter /usr/bin/python
New python executable in /tmp/zzz/bin/python
Installing setuptools, pip, wheel...done.
myhost:/tmp$ cd zzz
myhost:/tmp/zzz$ source bin/activate
(zzz) myhost:/tmp/zzz$ python -V
Python 2.7.12
(zzz) myhost:/tmp/zzz$ pip -V
pip 20.3.4 from /tmp/zzz/local/lib/python2.7/site-packages/pip (python 2.7)
(zzz) myhost:/tmp/zzz$ pip freeze
DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. pip 21.0 will drop support for Python 2.7 in January 2021. More details about Python 2 support in pip can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support pip 21.0 will remove support for this functionality.
(zzz) myhost:/tmp/zzz$ 

So the questions are

1. Why do I need to use virtualenv 15.0.1? Why can't I use a newer version of virtualenv?

2. How come python3 is complaining about the missing dataclasses module but python2 is ok?

Answer 1

Like mentioned in this pypi docs; https://pypi.org/project/dataclasses/ dataclasses only exist in 3.7 and above, which i would recommend to use instead, otherwise, you could also download this package in hopes that it fixes your problem. Are you limited to a python version?