Strip leading/trailing spaces/tabs from mirrors

If a Debian mirror has leading/trailing spaces/tabs, mmdebstrap will
fail:

```
I: running apt-get update...
E: Malformed entry 3 in list file /tmpfs/mmdebstrap.IQ6vCUfFh5/etc/apt/sources.list (URI parse)
E: The list of sources could not be read.
E: apt-get update -oAPT::Status-Fd=<$fd> -oDpkg::Use-Pty=false failed
I: main() received signal PIPE: waiting for setup...
W: listening on child socket failed: E: received eof on socket
```

Therefore strip leading/trailing spaces/tabs from the mirrors specified
with `--mirrors`.

Signed-off-by: Benjamin Drung <[email protected]>

bdebstrap

@@ -426,14 +426,16 @@ def parse_args(args):  # pylint: disable=too-many-statements
         args.components = [c for l in args.components for c in re.split(",| ", l) if c]
     if args.architectures:
         args.architectures = [a for l in args.architectures for a in re.split(",| ", l) if a]
-    args.mirrors = [m for mirror_list in args.mirrors for m in mirror_list.split(",") if m]
+    args.mirrors = [
+        m.strip() for mirror_list in args.mirrors for m in mirror_list.split(",") if m.strip()
+    ]
 
     # Positional arguments override optional arguments (or extent them in case of "mirrors")
     if args.suite_positional:
         args.suite = args.suite_positional
     if args.target_positional:
         args.target = args.target_positional
-    args.mirrors += [m for m in args.mirrors_positional if m]
+    args.mirrors += [m.strip() for m in args.mirrors_positional if m.strip()]
     del args.suite_positional
     del args.target_positional
     del args.mirrors_positional

tests/test_config.py

@@ -110,6 +110,28 @@ def test_malformed_env(self):
         with self.assertRaises(SystemExit):
             parse_args(["--env", "invalid"])
 
+    def test_mirrors_with_spaces(self):
+        """Test --mirrors with leading/trailing spaces."""
+        args = parse_args(
+            [
+                "--mirrors",
+                "  deb http://deb.debian.org/debian unstable main\t ,  \t, "
+                "deb http://deb.debian.org/debian unstable non-free\t",
+                "--mirrors",
+                "\tdeb http://deb.debian.org/debian unstable contrib ",
+            ]
+        )
+        self.assertDictContainsSubset(
+            {
+                "mirrors": [
+                    "deb http://deb.debian.org/debian unstable main",
+                    "deb http://deb.debian.org/debian unstable non-free",
+                    "deb http://deb.debian.org/debian unstable contrib",
+                ],
+            },
+            args.__dict__,
+        )
+
     def test_optional_args(self):
         """Test optional arguments (which also have positional ones)."""
         args = parse_args(