drop support for python 3.6

.github/workflows/build-test.yaml

@@ -19,10 +19,6 @@ jobs:
         dependencies: [full]
         tests-type: [unit]
         include:
-          - os: ubuntu-18.04
-            python-version: 3.6
-            dependencies: minimal
-            tests-type: unit
           - os: ubuntu-18.04
             python-version: 3.7
             dependencies: full

README.md

@@ -61,7 +61,7 @@ and work within a conda environment:
 
 ```
 # Create a conda environment named yt-git
-$ conda create -n yt-git python=3.6
+$ conda create -n yt-git python=3.8
 # Activate it
 $ source activate yt-git
 # Make sure you run the latest version of conda

pyproject.toml

@@ -3,17 +3,14 @@
 requires = [
   "setuptools>=19.6",
   "wheel",
-
-  # keep in sync with travis.yml "minimal" specs (Cython and numpy for py36)
   "Cython>=0.26.1",
-  "numpy==1.13.3; python_version=='3.6' and platform_system!='AIX'",
-  "numpy>=1.18.4; python_version>='3.7' and platform_system!='AIX'",
+  "numpy>=1.18.4; platform_system!='AIX'",
 ]
 
 # To be kept consistent with "Code Style" section in CONTRIBUTING.rst
 [tool.black]
 line-length = 88
-target-version = ['py36', 'py37', 'py38']
+target-version = ['py37', 'py38']
 include = '\.pyi?$'
 exclude = '''
 /(

setup.py

@@ -110,9 +110,6 @@ def has_ext_modules(self):
             "Operating System :: POSIX :: AIX",
             "Operating System :: POSIX :: Linux",
             "Programming Language :: C",
-            "Programming Language :: Python :: 3",
-            "Programming Language :: Python :: 3.5",
-            "Programming Language :: Python :: 3.6",
             "Programming Language :: Python :: 3.7",
             "Programming Language :: Python :: 3.8",
             "Topic :: Scientific/Engineering :: Astronomy",
@@ -153,5 +150,5 @@ def has_ext_modules(self):
         scripts=["scripts/iyt"],
         distclass=BinaryDistribution,
         ext_modules=[],  # !!! We override this inside build_ext above
-        python_requires=">=3.6",
+        python_requires=">=3.7",
     )

tests/ci_install.sh

@@ -52,6 +52,8 @@ if [[ ${dependencies} == "minimal" ]]; then
     # don't error out
     # The first numpy to support py3.6 is 1.12, but numpy 1.13 matches
     # unyt so we'll match it here.
+
+    # TODO: UPDATE THIS TO TARGET PYTHON 3.7 AS MINIMAL
     python -m pip install numpy==1.13.3 cython==0.26.1
     python -m pip install -r tests/test_minimal_requirements.txt
 else

yt/__init__.py

@@ -9,10 +9,9 @@
 """
 import sys
 
-if sys.version_info[0] < 3:
-    raise Exception(
-        "Python 2 no longer supported.  Please install Python 3 for use with yt."
-    )
+py_version = sys.version_info
+if not (py_version.major == 3 and py_version.minor >= 7):
+    raise sys.exit("yt requires Python 3.7 or later.")
 
 __version__ = "4.0.dev0"