pip.exceptions.InstallationError: Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-2g90f3pv-build/

Hi,
I have
Python 3.6
Ubuntu 18.04
torch installed via pip in version 1.2.0
CUDA 10.0
Driver Version: 418.56
CUDNN v7.6.4
gcc version 7.3.0 (Ubuntu 7.3.0-27ubuntu1~18.04)

With the command:
pip3 install -v --no-cache-dir --global-option="--cpp_ext" --global-option="--cuda_ext" ./

I get the following error message. Please any help is really appreciated.

/usr/lib/python3/dist-packages/pip/commands/install.py:212: UserWarning: Disabling all use of wheels due to the use of --build-options / --global-options / --install-options.
  cmdoptions.check_install_build_global(options)
Converted retries value: Retry(total=5, connect=None, read=None, redirect=None) -> Retry(total=Retry(total=5, connect=None, read=None, redirect=None), connect=None, read=None, redirect=None)
Converted retries value: Retry(total=5, connect=None, read=None, redirect=None) -> Retry(total=Retry(total=5, connect=None, read=None, redirect=None), connect=None, read=None, redirect=None)
Processing /media/alberto/50C03782C0376D7A/RSNA/apex
  Running setup.py (path:/tmp/pip-2g90f3pv-build/setup.py) egg_info for package from file:///media/alberto/50C03782C0376D7A/RSNA/apex
    Running command python setup.py egg_info
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-2g90f3pv-build/setup.py", line 5, in <module>
        from pip._internal import main as pipmain
    ModuleNotFoundError: No module named 'pip._internal'
Cleaning up...

Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-2g90f3pv-build/

Exception information:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/pip/basecommand.py", line 215, in main
    status = self.run(options, args)
  File "/usr/lib/python3/dist-packages/pip/commands/install.py", line 342, in run
    requirement_set.prepare_files(finder)
  File "/usr/lib/python3/dist-packages/pip/req/req_set.py", line 380, in prepare_files
    ignore_dependencies=self.ignore_dependencies))
  File "/usr/lib/python3/dist-packages/pip/req/req_set.py", line 634, in _prepare_file
    abstract_dist.prep_for_dist()
  File "/usr/lib/python3/dist-packages/pip/req/req_set.py", line 129, in prep_for_dist
    self.req_to_install.run_egg_info()
  File "/usr/lib/python3/dist-packages/pip/req/req_install.py", line 439, in run_egg_info
    command_desc='python setup.py egg_info')
  File "/usr/lib/python3/dist-packages/pip/utils/__init__.py", line 725, in call_subprocess
    % (command_desc, proc.returncode, cwd))
pip.exceptions.InstallationError: Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-2g90f3pv-build/

Start with setup.py line 5 and the exact pip3 install command shown in the report. Reproduce the failure on the listed Python, Ubuntu, and PyTorch versions, then trace why the build reaches the missing pip._internal module. Done means the Apex installation command completes successfully or the compatibility limitation is clearly documented.