feat(tests): Use subprocess.run

Simplify code by using `subprocess.run`.

tests/test_black.py

@@ -36,12 +36,9 @@ def test_black(self):
         cmd = ["black", "--check", "--diff"] + get_source_files()
         if unittest_verbosity() >= 2:
             sys.stderr.write(f"Running following command:\n{' '.join(cmd)}\n")
-        with subprocess.Popen(
-            cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, close_fds=True
-        ) as process:
-            output = process.communicate()[0].decode()
+        process = subprocess.run(cmd, capture_output=True, check=False, text=True)
 
         if process.returncode == 1:  # pragma: no cover
-            self.fail(f"black found code that needs reformatting:\n{output.strip()}")
+            self.fail(f"black found code that needs reformatting:\n{process.stdout.strip()}")
         if process.returncode != 0:  # pragma: no cover
-            self.fail(f"black exited with code {process.returncode}:\n{output.strip()}")
+            self.fail(f"black exited with code {process.returncode}:\n{process.stdout.strip()}")

tests/test_flake8.py

@@ -36,20 +36,17 @@ def test_flake8(self):
         cmd = [sys.executable, "-m", "flake8", "--max-line-length=99"] + get_source_files()
         if unittest_verbosity() >= 2:
             sys.stderr.write(f"Running following command:\n{' '.join(cmd)}\n")
-        with subprocess.Popen(
-            cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, close_fds=True
-        ) as process:
-            out, err = process.communicate()
+        process = subprocess.run(cmd, capture_output=True, check=False, text=True)
 
         if process.returncode != 0:  # pragma: no cover
             msgs = []
-            if err:
+            if process.stderr:
                 msgs.append(
-                    f"flake8 exited with code {process.returncode} "
-                    f"and has unexpected output on stderr:\n{err.decode().rstrip()}"
+                    f"flake8 exited with code {process.returncode} and has"
+                    f" unexpected output on stderr:\n{process.stderr.rstrip()}"
                 )
-            if out:
-                msgs.append(f"flake8 found issues:\n{out.decode().rstrip()}")
+            if process.stdout:
+                msgs.append(f"flake8 found issues:\n{process.stdout.rstrip()}")
             if not msgs:
                 msgs.append(
                     f"flake8 exited with code {process.returncode} "

tests/test_isort.py

@@ -36,10 +36,7 @@ def test_isort(self):
         cmd = ["isort", "--check-only", "--diff"] + get_source_files()
         if unittest_verbosity() >= 2:
             sys.stderr.write(f"Running following command:\n{' '.join(cmd)}\n")
-        with subprocess.Popen(
-            cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, close_fds=True
-        ) as process:
-            output = process.communicate()[0].decode()
+        process = subprocess.run(cmd, capture_output=True, check=False, text=True)
 
         if process.returncode != 0:  # pragma: no cover
-            self.fail(f"isort found unsorted Python import definitions:\n{output.strip()}")
+            self.fail(f"isort found unsorted Python import definitions:\n{process.stdout.strip()}")

tests/test_pylint.py

@@ -42,10 +42,7 @@ def test_pylint(self):
             cmd.insert(2, "--errors-only")
         if unittest_verbosity() >= 2:
             sys.stderr.write(f"Running following command:\n{' '.join(cmd)}\n")
-        with subprocess.Popen(
-            cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, close_fds=True
-        ) as process:
-            out, err = process.communicate()
+        process = subprocess.run(cmd, capture_output=True, check=False, text=True)
 
         if process.returncode != 0:  # pragma: no cover
             # Strip trailing summary (introduced in pylint 1.7). This summary might look like:
@@ -54,11 +51,11 @@ def test_pylint(self):
             # Your code has been rated at 10.00/10
             #
             out = re.sub(
-                "^(-+|Your code has been rated at .*)$", "", out.decode(), flags=re.MULTILINE
+                "^(-+|Your code has been rated at .*)$", "", process.stdout, flags=re.MULTILINE
             ).rstrip()
 
             # Strip logging of used config file (introduced in pylint 1.8)
-            err = re.sub("^Using config file .*\n", "", err.decode()).rstrip()
+            err = re.sub("^Using config file .*\n", "", process.stderr.rstrip())
 
             msgs = []
             if err: