Stop using Python 3.6 internally and in CI

build-support/bin/bootstrap_pants_pex.sh

@@ -5,7 +5,7 @@ cd "$REPO_ROOT" || exit 1
 
 # This script is used to generate pants.pex, which is used to run Pants in CI.
 
-export PY="${PY:-python3}"
+export PY="${PY:-python3.7}"
 
 # shellcheck source=build-support/common.sh
 source "${REPO_ROOT}/build-support/common.sh"

build-support/bin/ci.py

@@ -65,7 +65,6 @@ def main() -> None:
 
 
 class PythonVersion(Enum):
-    py36 = "3.6"
     py37 = "3.7"
 
     def __str__(self) -> str:
@@ -78,8 +77,8 @@ def create_parser() -> argparse.ArgumentParser:
         "--python-version",
         type=PythonVersion,
         choices=list(PythonVersion),
-        default=PythonVersion.py36,
-        help="Run Pants with this version (defaults to 3.6).",
+        default=PythonVersion.py37,
+        help="Run Pants with this version.",
     )
     parser.add_argument(
         "--remote-execution-enabled",

build-support/bin/generate_travis_yml.py

@@ -77,7 +77,6 @@ def all_entries(cls) -> List[Dict[str, str]]:
     "BOOTSTRAPPED_PEX_KEY_PREFIX=daily/${TRAVIS_BUILD_NUMBER}/${TRAVIS_BUILD_ID}/pants.pex",
     "NATIVE_ENGINE_SO_KEY_PREFIX=monthly/native_engine_so",
     "MACOS_PYENV_PY27_VERSION=2.7.18",
-    "MACOS_PYENV_PY36_VERSION=3.6.10",
     "MACOS_PYENV_PY37_VERSION=3.7.7",
     "MACOS_PYENV_PY38_VERSION=3.8.3",
     # NB: We must set `PYENV_ROOT` on macOS for Pyenv to work properly. However, on Linux, we must not
@@ -111,7 +110,6 @@ def all_entries(cls) -> List[Dict[str, str]]:
 
 
 class PythonVersion(Enum):
-    py36 = "py36"
     py37 = "py37"
     py38 = "py38"
 
@@ -120,24 +118,16 @@ def __str__(self) -> str:
 
     @property
     def number(self) -> int:
-        return {self.py36: 36, self.py37: 37, self.py38: 38}[self]  # type: ignore[index]
+        return {self.py37: 37, self.py38: 38}[self]  # type: ignore[index]
 
     @property
     def decimal(self) -> float:
-        return {self.py36: 3.6, self.py37: 3.7, self.py38: 3.8}[self]  # type: ignore[index]
+        return {self.py37: 3.7, self.py38: 3.8}[self]  # type: ignore[index]
 
     def default_stage(self, *, is_bootstrap: bool = False) -> Stage:
         if is_bootstrap:
-            return {
-                self.py36: Stage.bootstrap,
-                self.py37: Stage.bootstrap_cron,
-                self.py38: Stage.bootstrap_cron,
-            }[
-                self  # type: ignore[index]
-            ]
-        return {self.py36: Stage.test, self.py37: Stage.test_cron, self.py38: Stage.test_cron,}[
-            self  # type: ignore[index]
-        ]
+            return {self.py37: Stage.bootstrap, self.py38: Stage.bootstrap_cron}[self]  # type: ignore[index]
+        return {self.py37: Stage.test, self.py38: Stage.test_cron}[self]  # type: ignore[index]
 
 
 # ----------------------------------------------------------------------
@@ -291,7 +281,7 @@ def _linux_before_install(
 def linux_shard(
     *,
     load_test_config: bool = True,
-    python_version: PythonVersion = PythonVersion.py36,
+    python_version: PythonVersion = PythonVersion.py37,
     use_docker: bool = False,
     install_travis_wait: bool = False,
 ) -> Dict:
@@ -377,7 +367,6 @@ def _osx_env_with_pyenv() -> List[str]:
     return [
         *_osx_env(),
         'PATH="${PYENV_ROOT}/versions/${MACOS_PYENV_PY27_VERSION}/bin:${PATH}"',
-        'PATH="${PYENV_ROOT}/versions/${MACOS_PYENV_PY36_VERSION}/bin:${PATH}"',
         'PATH="${PYENV_ROOT}/versions/${MACOS_PYENV_PY37_VERSION}/bin:${PATH}"',
         'PATH="${PYENV_ROOT}/versions/${MACOS_PYENV_PY38_VERSION}/bin:${PATH}"',
     ]
@@ -386,7 +375,7 @@ def _osx_env_with_pyenv() -> List[str]:
 def osx_shard(
     *,
     load_test_config: bool = True,
-    python_version: PythonVersion = PythonVersion.py36,
+    python_version: PythonVersion = PythonVersion.py37,
     osx_image: Optional[str] = None,
 ) -> Dict:
     setup = {
@@ -607,10 +596,9 @@ def rust_tests_linux() -> Dict:
         "name": "Rust tests - Linux",
         "env": [
             "CACHE_NAME=rust_tests.linux",
-            # TODO: Despite being successfully linked at build time, the Linux rust tests
-            # shard is unable to locate `libpython3.6m.so.1.0` at runtime without this pointer:
-            # OSX appears to be fine.
-            'LD_LIBRARY_PATH="/opt/python/3.6.7/lib:${LD_LIBRARY_PATH}"',
+            # Despite being successfully linked at build time, the Linux Rust tests are unable to
+            # locate libpython3.7m.so.1.0 at runtime without this pointer.
+            'LD_LIBRARY_PATH="/opt/python/3.7.1/lib:${LD_LIBRARY_PATH}"',
         ],
     }
 
@@ -628,7 +616,7 @@ def rust_tests_osx() -> Dict:
         #      See https://gist.github.com/stuhood/856a9b09bbaa86141f36c9925c14fae7
         "osx_image": "xcode8",
         "before_install": [
-            './build-support/bin/install_python_for_ci.sh "${MACOS_PYENV_PY36_VERSION}"',
+            './build-support/bin/install_python_for_ci.sh "${MACOS_PYENV_PY37_VERSION}"',
             # We don't use the standard travis "addons" section here because it will either silently
             # fail (on older images) or cause a multi-minute `brew update` (on newer images), neither of
             # which we want. This doesn't happen if we just manually run `brew cask install`.
@@ -772,7 +760,7 @@ def ignore_aliases(self, data):
 
 
 def main() -> None:
-    supported_python_versions = [PythonVersion.py36, PythonVersion.py37]
+    supported_python_versions = [PythonVersion.py37]
     generated_yaml = yaml.dump(
         {
             # Conditions are documented here: https://docs.travis-ci.com/user/conditions-v1

build-support/bin/native/cargo.sh

@@ -6,7 +6,7 @@ set -euo pipefail
 
 REPO_ROOT=$(cd "$(dirname "${BASH_SOURCE[0]}")" && cd ../../.. && pwd -P)
 
-export PY=${PY:-python3}
+export PY=${PY:-python3.7}
 # Consumed by the cpython crate.
 export PYTHON_SYS_EXECUTABLE="${PY}"
 

build-support/bin/native/print_engine_hash.sh

@@ -10,7 +10,7 @@
  # shellcheck source=build-support/pants_venv
  source "${REPO_ROOT}/build-support/pants_venv"
 
- export PY="${PY:-python3}"
+ export PY="${PY:-python3.7}"
  activate_pants_venv 1>&2  # Redirect to ensure that we don't interfere with stdout.
 
  calculate_current_hash

build-support/bin/upload_coverage.sh

@@ -1,6 +1,6 @@
 #!/bin/bash -e
 
-export PY=${PY:-python3}
+export PY=${PY:-python3.7}
 export PYTHON_SYS_EXECUTABLE="${PY}"
 
 REPO_ROOT=$(cd "$(dirname "${BASH_SOURCE[0]}")" && cd ../.. && pwd -P)

build-support/pants_venv

@@ -25,14 +25,8 @@ function activate_venv() {
   source "$(venv_dir)/bin/activate"
 }
 
-function remove_venv() {
-  rm -rf "$(venv_dir)"
-  # Also remove legacy folders.
-  rm -rf "${venv_dir_prefix}.venv" "${venv_dir_prefix}.py{2,3}.venv"
-}
-
 function create_venv() {
-  remove_venv
+  rm -rf "$(venv_dir)"
   "${REPO_ROOT}/build-support/virtualenv" "$(venv_dir)"
 }
 
@@ -42,7 +36,7 @@ function ensure_gcc() {
 ERROR: unable to execute 'gcc'. Please verify that your compiler is installed, in your
        \$PATH and functional.
 
-Hint: on Mac OS X, you may need to accept the XCode EULA: 'sudo xcodebuild -license accept'.
+Hint: on macOS, you may need to accept the XCode EULA: 'sudo xcodebuild -license accept'.
 MESSAGE
 )"
   fi

pants

@@ -32,8 +32,8 @@
 # WRAPPER_SRCPATH=/src/wrapper/src/main/python \
 #    exec /src/pantsbuild-pants/pants "$@"
 #
-# The script defaults to running with Python 3. To use a specific Python version,
-# such as 3.7, prefix the script with `PY=python3.7`.
+# The script defaults to running with Python 3.7. To use another Python version,
+# such as 3.8, prefix the script with `PY=python3.8`.
 
 set -e
 
@@ -57,7 +57,7 @@ source "${HERE}/build-support/pants_venv"
 # shellcheck source=build-support/bin/native/bootstrap_code.sh
 source "${HERE}/build-support/bin/native/bootstrap_code.sh"
 
-export PY="${PY:-python3}"
+export PY="${PY:-python3.7}"
 
 PANTS_EXE="${HERE}/src/python/pants/bin/pants_loader.py"
 

pants.toml

@@ -54,6 +54,7 @@ root_patterns = [
 [python-setup]
 requirement_constraints = "3rdparty/python/constraints.txt"
 resolve_all_constraints = "nondeployables"
+interpreter_constraints = [">=3.7,<3.9"]
 
 [black]
 config = "pyproject.toml"