gh-40252: Don't install sage/tests/cmdline.py with meson
    
It contains tests that are not relevant for the meson build

We extract the `test_executable` function to `__init__.py`, since it is
still used in other files, and leave only the tests in `cmdline.py`.
    
URL: #40252
Reported by: Antonio Rojas
Reviewer(s): Tobias Diez

Author: Release Manager

src/sage/repl/interpreter.py

@@ -722,7 +722,7 @@ def get_test_shell():
 
     Check that :issue:`14070` has been resolved::
 
-        sage: from sage.tests.cmdline import test_executable
+        sage: from sage.tests import test_executable
         sage: cmd = 'from sage.repl.interpreter import get_test_shell; shell = get_test_shell()'
         sage: (out, err, ret) = test_executable(["sage", "-c", cmd])
         sage: out + err

src/sage/tests/__init__.py

@@ -0,0 +1,117 @@
+from subprocess import Popen, PIPE
+import os
+import sys
+import select
+
+
+def test_executable(args, input='', timeout=100.0, pydebug_ignore_warnings=False, **kwds):
+    r"""
+    Run the program defined by ``args`` using the string ``input`` on
+    the standard input.
+
+    INPUT:
+
+    - ``args`` -- list of program arguments, the first being the
+      executable
+
+    - ``input`` -- string serving as standard input; usually, this
+      should end with a newline
+
+    - ``timeout`` -- if the program produces no output for ``timeout``
+      seconds, a :exc:`RuntimeError` is raised
+
+    - ``pydebug_ignore_warnings`` -- boolean. Set the PYTHONWARNINGS environment variable to ignore
+      Python warnings when on a Python debug build (`--with-pydebug`, e.g. from building with
+      `SAGE_DEBUG=yes`). Debug builds do not install the default warning filters, which can break
+      some doctests. Unfortunately the environment variable does not support regex message filters,
+      so the filter will catch a bit more than the default filters. Hence we only enable it on debug
+      builds.
+
+    - ``**kwds`` -- additional keyword arguments passed to the
+      :class:`Popen` constructor
+
+    OUTPUT: a tuple ``(out, err, ret)`` with the standard output,
+    standard error and exitcode of the program run.
+
+    EXAMPLES::
+
+        sage: from sage.tests import test_executable
+        sage: (out, err, ret) = test_executable(["cat"], "Hello World!")
+        sage: out
+        'Hello World!'
+        sage: err
+        ''
+        sage: ret
+        0
+
+    We test the timeout option::
+
+        sage: (out, err, ret) = test_executable(["sleep", "1"], timeout=0.1)
+        Traceback (most recent call last):
+        ...
+        RuntimeError: timeout in test_executable()
+    """
+    pexpect_env = dict(os.environ)
+    try:
+        del pexpect_env["TERM"]
+    except KeyError:
+        pass
+
+    __with_pydebug = hasattr(sys, 'gettotalrefcount')   # This is a Python debug build (--with-pydebug)
+    if __with_pydebug and pydebug_ignore_warnings:
+        pexpect_env['PYTHONWARNINGS'] = ','.join([
+            'ignore::DeprecationWarning',
+        ])
+
+    kwds['encoding'] = kwds.pop('encoding', 'utf-8')
+
+    p = Popen(args, stdin=PIPE, stdout=PIPE, stderr=PIPE, env=pexpect_env,
+              **kwds)
+    if input:
+        p.stdin.write(input)
+
+    p.stdin.close()
+    fdout = p.stdout.fileno()
+    fderr = p.stderr.fileno()
+    out = []
+    err = []
+
+    while True:
+        # Try reading from fdout and fderr
+        rfd = []
+        if fdout:
+            rfd.append(fdout)
+        if fderr:
+            rfd.append(fderr)
+        if len(rfd) == 0:
+            break
+        timeout = float(timeout)
+        rlist = select.select(rfd, [], [], timeout)[0]
+
+        if len(rlist) == 0:
+            # Timeout!
+            p.terminate()
+            raise RuntimeError("timeout in test_executable()")
+        if fdout in rlist:
+            s = p.stdout.read(1024)
+            if not s:
+                fdout = None   # EOF
+                p.stdout.close()
+            out.append(s)
+        if fderr in rlist:
+            s = p.stderr.read(1024)
+            if not s:
+                fderr = None   # EOF
+                p.stderr.close()
+            err.append(s)
+
+    # In case out or err contains a quoted string, force the use of
+    # double quotes so that the output is enclosed in single
+    # quotes. This avoids some doctest failures with some versions of
+    # OS X and Xcode.
+    out = ''.join(out)
+    out = out.replace("'", '"')
+    err = ''.join(err)
+    err = err.replace("'", '"')
+
+    return (out, err, p.wait())