docs: remove metions of legacy python in docs and scripts

benchmarks/asv.conf.json

@@ -25,7 +25,7 @@
 
     // The Pythons you'd like to test against.  If not provided, defaults
     // to the current version of Python used to run `asv`.
-    // "pythons": ["2.7", "3.3"],
+    // "pythons": ["3.7", "3.8"],
 
     // The matrix of dependencies to test.  Each key is the name of a
     // package (in PyPI) and the values are version numbers.  An empty

doc/activate

@@ -70,8 +70,6 @@ YT_DEST="$VIRTUAL_ENV"
 export YT_DEST
 
 _OLD_VIRTUAL_PYTHONPATH="$PYTHONPATH"
-PYTHONPATH="$VIRTUAL_ENV/lib/python2.7/site-packages"
-export PYTHONPATH
 
 _OLD_VIRTUAL_LD_LIBRARY_PATH="$LD_LIBRARY_PATH"
 LD_LIBRARY_PATH="$VIRTUAL_ENV/lib:$LD_LIBRARY_PATH"

doc/install_script.sh

@@ -24,9 +24,6 @@ YT_DIR=""
 
 # These options can be set to customize the installation.
 
-INST_PY3=1      # Install Python 3 instead of Python 2. If this is turned on,
-                # all Python packages (including yt) will be installed
-                # in Python 3.
 INST_GIT=1      # Install git or not?  If git is not already installed, yt
                 # cannot be installed from source.
 INST_EMBREE=0   # Install dependencies needed for Embree-accelerated ray tracing
@@ -39,7 +36,6 @@ INST_CARTOPY=0  # Install cartopy?
 INST_NOSE=1     # Install nose?
 INST_NETCDF4=1  # Install netcdf4 and its python bindings?
 INST_POOCH=1    # Install pooch?
-INST_HG=0       # Install Mercurial or not?
 
 # This is the branch we will install from for INST_YT_SOURCE=1
 BRANCH="master"
@@ -383,12 +379,8 @@ function do_exit
     exit 1
 }
 
-if [ $INST_PY3 -eq 1 ]
-then
-     PYTHON_EXEC='python3'
-else 
-     PYTHON_EXEC='python2.7'
-fi
+PYTHON_EXEC='python3'
+
 
 if type -P curl &>/dev/null
 then
@@ -440,12 +432,7 @@ else
     exit 1
 fi
 
-if [ $INST_PY3 -eq 1 ]
-then
-    PY_VERSION='3'
-else
-    PY_VERSION='2'
-fi
+PY_VERSION='3'
 
 MINICONDA_PKG="Miniconda${PY_VERSION}-${MINICONDA_VERSION}-${MINICONDA_OS}-${MINICONDA_ARCH}.sh"
 
@@ -516,10 +503,6 @@ then
     YT_DEPS+=('pooch')
 fi
 YT_DEPS+=('conda-build')
-if [ $INST_PY3 -eq 0 ] && [ $INST_HG -eq 1 ]
-then
-    YT_DEPS+=('mercurial')
-fi
 YT_DEPS+=('sympy')
 
 if [ $INST_NETCDF4 -eq 1 ]
@@ -551,13 +534,6 @@ for YT_DEP in "${YT_DEPS[@]}"; do
     log_cmd ${DEST_DIR}/bin/conda install -c conda-forge --yes ${YT_DEP}
 done
 
-if [ $INST_PY3 -eq 1 ] && [ $INST_HG -eq 1 ]
-then
-    echo "Installing mercurial"
-    log_cmd ${DEST_DIR}/bin/conda create -y -n py27 python=2.7 mercurial
-    log_cmd ln -s ${DEST_DIR}/envs/py27/bin/hg ${DEST_DIR}/bin
-fi
-
 if [ $INST_YT_SOURCE -eq 1 ]
 then
     log_cmd ${GIT_EXE} clone https://github.com/yt-project/yt_conda ${DEST_DIR}/src/yt_conda
@@ -594,12 +570,7 @@ fi
 # conda doesn't package pyx, so we install manually with pip
 if [ $INST_PYX -eq 1 ]
 then
-    if [ $INST_PY3 -eq 1 ]
-    then
-        log_cmd ${DEST_DIR}/bin/pip install pyx
-    else
-        log_cmd ${DEST_DIR}/bin/pip install pyx==0.12.1
-    fi
+    log_cmd ${DEST_DIR}/bin/pip install pyx
 fi
 
 if [ $INST_YT_SOURCE -eq 0 ]

doc/source/analyzing/parallel_computation.rst

@@ -110,7 +110,7 @@ processes using the following Bash command:
 
 .. code-block:: bash
 
-   $ mpirun -np 16 python2.7 my_script.py
+   $ mpirun -np 16 python my_script.py
 
 .. note::
 

doc/source/developing/debugdrive.rst

@@ -99,7 +99,7 @@ provided through the yt command.  So if you run the command:
 
 .. code-block:: bash
 
-   $ mpirun -np 4 python2.7 some_script.py --parallel --rpdb
+   $ mpirun -np 4 python some_script.py --parallel --rpdb
 
 and it reaches an error or an exception, it will launch the debugger.
 Additionally, instructions will be printed for connecting to the debugger.

doc/source/developing/external_analysis.rst

@@ -188,7 +188,7 @@ To build our extension, we would run:
 
 .. code-block:: bash
 
-   $ python2.7 axes_calculator_setup.py build_ext -i
+   $ python axes_calculator_setup.py build_ext -i
 
 Note that since we don't yet have an ``axes_calculator.pyx``, this will fail.
 But once we have it, it ought to run.

doc/source/developing/testing.rst

@@ -496,19 +496,3 @@ In order to add a new set of answer tests, it is sufficient to extend the
    +
     other_tests:
       unittests:
-
-Restricting Python Versions for Answer Tests
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-If for some reason a test can be run only for a specific version of python it is
-possible to indicate this by adding a ``[py2]`` or ``[py3]`` tag. For example:
-
-.. code-block:: yaml
-
-   answer_tests:
-      local_test_000:
-         - yt/test_A.py  # [py2]
-         - yt/test_B.py  # [py3]
-
-would result in ``test_A.py`` being run only for *python2* and ``test_B.py``
-being run only for *python3*.

doc/source/installing.rst

@@ -413,8 +413,8 @@ development version of yt instead of the latest stable release, you will need
   if you are curious why ``--install-option="--prefix="`` is necessary on some systems.
 
 This will install yt into a folder in your home directory
-(``$HOME/.local/lib64/python2.7/site-packages`` on Linux,
-``$HOME/Library/Python/2.7/lib/python/site-packages/`` on OSX) Please refer to
+(e.g. ``$HOME/.local/lib64/python<py_version>/site-packages`` on Linux,
+``$HOME/Library/Python/<py_version>/lib/python/site-packages/`` on OSX) Please refer to
 the ``setuptools`` documentation for the additional options.
 
 If you are unable to locate the ``yt`` executable (i.e. executing ``yt version``

setup.py

@@ -140,5 +140,5 @@
         zip_safe=False,
         scripts=["scripts/iyt"],
         ext_modules=[],  # !!! We override this inside build_ext above
-        python_requires=">=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*",
+        python_requires=">=3.6",
     )