Readd test that sage.all imports without error in new session

Author: tobiasdiez

src/sage/all_test.py

@@ -0,0 +1,28 @@
+import os
+import subprocess
+import sys
+
+
+def test_import_sage_all_in_fresh_interpreter():
+    # Prepare a clean-ish environment, without any sage variables
+    env = os.environ.copy()
+    env.pop("PYTHONSTARTUP", None)
+    for var in list(env):
+        if var.startswith("SAGE_"):
+            env.pop(var, None)
+
+    proc = subprocess.run(
+        [sys.executable, "-c", "import sage.all"],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+        env=env,
+        text=True, check=False,
+    )
+    assert proc.returncode == 0, (
+        "Importing 'sage.all' in a fresh interpreter failed.\n"
+        f"Return code: {proc.returncode}\n"
+        f"Stdout:\n{proc.stdout}\n"
+        f"Stderr:\n{proc.stderr}"
+    )
+    assert proc.stderr == ""
+    assert proc.stdout == ""