conn: use /usr/bin/env to run the shell

To make the code more portable to distributions that don't have
bash in /usr/bin.

Resolves: next-actions#95

Link: <shadow-maint/shadow#1131>
Reported-by: Iker Pedrosa <ipedrosa@redhat.com>
Reported-by: Alejandro Colomar <alx@kernel.org>
Suggested-by: Alejandro Colomar <alx@kernel.org>

pytest_mh/conn/__init__.py

@@ -1037,7 +1037,7 @@ class Bash(Shell):
     """
 
     def __init__(self) -> None:
-        super().__init__("bash", "/usr/bin/bash -c")
+        super().__init__("bash", "/usr/bin/env bash -c")
 
     def build_command_line(self, script: str, *, cwd: str | None, env: dict[str, Any]) -> str:
         full_script = self._add_cwd_and_env(script, cwd=cwd, env=env)
@@ -1065,7 +1065,7 @@ def _add_cwd_and_env(self, script: str, *, cwd: str | None, env: dict[str, Any])
 
     def _escape_single_quotes(self, command: str) -> str:
         """
-        We call the command as `bash -c '$command'`.
+        We call the command as `/usr/bin/env bash -c '$command'`.
 
         We need to escape ' inside the script to make it work correctly.
         """

tests/test_conn.py

@@ -24,7 +24,7 @@ def test_conn__shell_bash__script(input: str, expected: str):
     shell = Bash()
 
     assert shell.name == "bash"
-    assert shell.shell_command == "/usr/bin/bash -c"
+    assert shell.shell_command == "/usr/bin/env bash -c"
 
     cmd = shell.build_command_line(input, cwd=None, env={})
     assert cmd == f"{shell.shell_command} '{expected}'"
@@ -34,7 +34,7 @@ def test_conn__shell_bash__cwd():
     shell = Bash()
 
     assert shell.name == "bash"
-    assert shell.shell_command == "/usr/bin/bash -c"
+    assert shell.shell_command == "/usr/bin/env bash -c"
 
     cmd = shell.build_command_line("echo hello world", cwd="/home/test", env={})
     expected = textwrap.dedent(
@@ -51,7 +51,7 @@ def test_conn__shell_bash__env():
     shell = Bash()
 
     assert shell.name == "bash"
-    assert shell.shell_command == "/usr/bin/bash -c"
+    assert shell.shell_command == "/usr/bin/env bash -c"
 
     cmd = shell.build_command_line("echo hello world", cwd=None, env={"HELLO": "WORLD", "JOHN": "DOE"})
     expected = textwrap.dedent(
@@ -69,7 +69,7 @@ def test_conn__shell_bash__cwd_env():
     shell = Bash()
 
     assert shell.name == "bash"
-    assert shell.shell_command == "/usr/bin/bash -c"
+    assert shell.shell_command == "/usr/bin/env bash -c"
 
     cmd = shell.build_command_line("echo hello world", cwd="/home/test", env={"HELLO": "WORLD", "JOHN": "DOE"})
     expected = textwrap.dedent(