Dependencies: Python incl. venv

Backported from #2556.

Follow-up to #2653

Docs/source/developers/testing.rst

@@ -77,8 +77,9 @@ Add a test to the suite
 There are three steps to follow to add a new automated test (illustrated here for PML boundary conditions):
 
 * An input file for your test, in folder `Example/Tests/...`. For the PML test, the input file is at ``Examples/Tests/PML/inputs_2d``. You can also re-use an existing input file (even better!) and pass specific parameters at runtime (see below).
-* A Python script that reads simulation output and tests correctness versus theory or calibrated results. For the PML test, see ``Examples/Tests/PML/analysis_pml_yee.py``. It typically ends with Python statement `assert( error<0.01 )`.
-* Add an entry to [Regression/WarpX-tests.ini](./Regression/WarpX-tests.ini), so that a WarpX simulation runs your test in the continuous integration process, and the Python script is executed to assess the correctness. For the PML test, the entry is
+* A Python script that reads simulation output and tests correctness versus theory or calibrated results. For the PML test, see ``Examples/Tests/PML/analysis_pml_yee.py``. It typically ends with Python statement ``assert( error<0.01 )``.
+* If you need a new Python package dependency for testing, add it in ``Regression/requirements.txt``
+* Add an entry to ``Regression/WarpX-tests.ini``, so that a WarpX simulation runs your test in the continuous integration process, and the Python script is executed to assess the correctness. For the PML test, the entry is
 
 .. code-block::
 

Docs/source/install/dependencies.rst

@@ -25,6 +25,13 @@ Optional dependencies include:
   - see `optional I/O backends <https://github.com/openPMD/openPMD-api#dependencies>`__
 - `CCache <https://ccache.dev>`__: to speed up rebuilds (For CUDA support, needs version 3.7.9+ and 4.2+ is recommended)
 - `Ninja <https://ninja-build.org>`__: for faster parallel compiles
+- `Python 3.6+ <https://www.python.org>`__
+
+  - `mpi4py <https://mpi4py.readthedocs.io>`__
+  - `numpy <https://numpy.org>`__
+  - `periodictable <https://periodictable.readthedocs.io>`__
+  - `picmistandard <https://picmi-standard.github.io>`__
+  - see our ``requirements.txt`` file for compatible versions
 
 
 Install
@@ -67,7 +74,7 @@ If you also want to run runtime tests and added Python (``spack add python`` and
 
 .. code-block:: bash
 
-   python -m pip install matplotlib==3.2.2 yt scipy numpy openpmd-api
+   python3 -m pip install matplotlib==3.2.2 yt scipy numpy openpmd-api virtualenv
 
 If you want to run the ``./run_test.sh`` :ref:`test script <developers-testing>`, which uses our legacy GNUmake build system, you need to set the following environment hints after ``spack env activate warpx-dev`` for dependent software:
 
@@ -118,7 +125,7 @@ Without MPI:
 
 .. code-block:: bash
 
-   conda create -n warpx-dev -c conda-forge blaspp ccache cmake compilers git lapackpp openpmd-api python numpy scipy yt fftw matplotlib mamba ninja
+   conda create -n warpx-dev -c conda-forge blaspp ccache cmake compilers git lapackpp openpmd-api python numpy scipy yt fftw matplotlib mamba ninja pip virtualenv
    source activate warpx-dev
 
    # compile WarpX with -DWarpX_MPI=OFF
@@ -127,7 +134,7 @@ With MPI (only Linux/macOS):
 
 .. code-block:: bash
 
-   conda create -n warpx-dev -c conda-forge blaspp ccache cmake compilers git lapackpp "openpmd-api=*=mpi_openmpi*" python numpy scipy yt "fftw=*=mpi_openmpi*" matplotlib mamba ninja openmpi
+   conda create -n warpx-dev -c conda-forge blaspp ccache cmake compilers git lapackpp "openpmd-api=*=mpi_openmpi*" python numpy scipy yt "fftw=*=mpi_openmpi*" matplotlib mamba ninja openmpi pip virtualenv
    source activate warpx-dev
 
 For legacy ``GNUmake`` builds, after each ``source activate warpx-dev``, you also need to set:
@@ -145,7 +152,7 @@ Apt (Debian/Ubuntu)
 .. code-block:: bash
 
    sudo apt update
-   sudo apt install build-essential ccache cmake g++ git libfftw3-mpi-dev libfftw3-dev libhdf5-openmpi-dev libopenmpi-dev pkg-config python3 python3-matplotlib python3-numpy python3-scipy
+   sudo apt install build-essential ccache cmake g++ git libfftw3-mpi-dev libfftw3-dev libhdf5-openmpi-dev libopenmpi-dev pkg-config python3 python3-matplotlib python3-numpy python3-pip python3-scipy python3-venv
 
    # optional:
    # for CUDA, either install