coveralls is unable to sent report to coveralls.io and bagde is still "unknow"

Question

I still faced trouble configuring coveralls. Coveralls successfully run in Travis CI and the report is visible BUT, after success, the following error occurs:

---------- coverage: platform linux, python 3.7.10-final-0 -----------
Name                                    Stmts   Miss Branch BrPart  Cover
-------------------------------------------------------------------------
tests/__init__.py                          24      1      4      1    93%
tests/core/__init__.py                      0      0      0      0   100%
tests/core/test_core.py                   192     38     84     13    81%
tests/geodrill/__init__.py                 19     16     10      0    10%
tests/geodrill/test_geodrill.py           106     30     48     10    70%
tests/modeling/__init__.py                 42      5     18      3    87%
tests/modeling/test_occam2d_models.py     100     13     46      5    86%
tests/processing/__init__.py               10      0      2      0   100%
tests/processing/test_processing.py        47      7     18      2    86%
-------------------------------------------------------------------------
TOTAL                                     540    110    230     34    79%
0.03s$ coveralls
Traceback (most recent call last):
  File "/home/travis/miniconda/envs/test-env/bin/coveralls", line 5, in <module>
    from coveralls.cli import main
ModuleNotFoundError: No module named 'coveralls.cli'

Consequently, my repo coveralls badge is still unknown, and no report is visible on my coveralls.io account.

I configured my .travis.yml as follow ;

dist: xenial
sudo: required

language: python
python:
  - "3.7"

before_script: null

before_install:
    - python -m pip install --upgrade pip

install:
    - wget https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O miniconda.sh;
    - bash miniconda.sh -b -p $HOME/miniconda
    - export PATH="$HOME/miniconda/bin:$PATH"
    - hash -r
    - conda config --set always_yes yes --set changeps1 no
    - conda update -q conda
    - conda info -a
    - conda create -q -n test-env python=$TRAVIS_PYTHON_VERSION pytest pytest-cov pyyaml
    - source activate test-env
    - pip install --user -r requirements.txt                       
    - pip install configparser
    - pip install coveralls 

script: 
   
    - python -m pytest --cov=tests --cov-fail-under=50      # coveral fail threshold 50%
    
after_success:
  - coveralls 
  

Could anyone help me to fix it? thanks in advance!