Use pytest parallelisation if available.

Backported to 0.51.2

.travis.yml

@@ -63,4 +63,4 @@ script:
           /bin/sh -c "cd /root && mkdir -p tools; wget -c http://nirbheek.in/files/binaries/ninja/linux-amd64/ninja -O /root/tools/ninja; chmod +x /root/tools/ninja; CC=$CC CXX=$CXX OBJC=$CC OBJCXX=$CXX PATH=/root/tools:$PATH MESON_FIXED_NINJA=1 ./run_tests.py $RUN_TESTS_ARGS -- $MESON_ARGS && chmod -R a+rwX .coverage"
     fi
   # Ensure that llvm is added after $PATH, otherwise the clang from that llvm install will be used instead of the native apple clang.
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then SDKROOT=$(xcodebuild -version -sdk macosx Path) CPPFLAGS=-I/usr/local/include LDFLAGS=-L/usr/local/lib OBJC=$CC OBJCXX=$CXX PATH=$HOME/tools:/usr/local/opt/qt/bin:$PATH:$(brew --prefix llvm)/bin MESON_FIXED_NINJA=1 ./run_tests.py --backend=ninja -- $MESON_ARGS ; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then SDKROOT=$(xcodebuild -version -sdk macosx Path) CPPFLAGS=-I/usr/local/include LDFLAGS=-L/usr/local/lib OBJC=$CC OBJCXX=$CXX PATH=$HOME/tools:/usr/local/opt/qt/bin:$PATH:$(brew --prefix llvm)/bin MESON_FIXED_NINJA=1 ./run_tests.py $RUN_TESTS_ARGS --backend=ninja -- $MESON_ARGS ; fi

run_project_tests.py

@@ -790,6 +790,10 @@ def check_format():
     for (root, _, files) in os.walk('.'):
         if '.dub' in root: # external deps are here
             continue
+        if '.pytest_cache' in root:
+            continue
+        if 'meson-logs' in root or 'meson-private' in root:
+            continue
         for fname in files:
             if os.path.splitext(fname)[1].lower() in check_suffixes:
                 bn = os.path.basename(fname)

run_unittests.py

@@ -3350,7 +3350,7 @@ recommended as it is not supported on some platforms''')
 
         for entry in res:
             name = entry['name']
-            self.assertEquals(entry['subproject'], expected[name])
+            self.assertEqual(entry['subproject'], expected[name])
 
     def test_introspect_projectinfo_subproject_dir(self):
         testdir = os.path.join(self.common_test_dir, '79 custom subproject dir')
@@ -6413,6 +6413,17 @@ def unset_envs():
 
 def main():
     unset_envs()
+    pytest_args = ['-n', 'auto', './run_unittests.py']
+    if shutil.which('pytest-3'):
+        return subprocess.run(['pytest-3'] + pytest_args).returncode
+    elif shutil.which('pytest'):
+        return subprocess.run(['pytest'] + pytest_args).returncode
+    try:
+        import pytest # noqa: F401
+        return subprocess.run(python_command + ['-m', 'pytest'] + pytest_args).returncode
+    except ImportError:
+        pass
+    # All attempts at locating pytest failed, fall back to plain unittest.
     cases = ['InternalTests', 'DataTests', 'AllPlatformTests', 'FailureTests',
              'PythonTests', 'NativeFileTests', 'RewriterTests', 'CrossFileTests',
              'TAPParserTests',