Merge pull request #291 from dhellmann/fix-network-isolation-test

improve network isolation error handling

src/fromager/external_commands.py

@@ -41,6 +41,10 @@ def detect_network_isolation():
         subprocess.check_call(check, stderr=subprocess.STDOUT)
 
 
+class NetworkIsolationError(subprocess.CalledProcessError):
+    pass
+
+
 # based on pyproject_hooks/_impl.py: quiet_subprocess_runner
 def run(
     cmd: typing.Sequence[str],
@@ -92,6 +96,17 @@ def run(
         output = completed.stdout.decode("utf-8") if completed.stdout else ""
     if completed.returncode != 0:
         logger.error("%s failed with %s", cmd, output)
-        raise subprocess.CalledProcessError(completed.returncode, cmd, output)
+        err_type = subprocess.CalledProcessError
+        if network_isolation:
+            # Look for a few common messages that mean there is a network
+            # isolation problem and change the exception type to make it easier
+            # for the caller to recognize that case.
+            for substr in [
+                "network unreachable",
+                "Network is unreachable",
+            ]:
+                if substr in output:
+                    err_type = NetworkIsolationError
+        raise err_type(completed.returncode, cmd, output)
     logger.debug("output: %s", output)
     return output

tests/test_external_commands.py

@@ -73,12 +73,11 @@ def test_external_commands_network_isolation(
     not SUPPORTS_NETWORK_ISOLATION, reason="network isolation is not supported"
 )
 def test_external_commands_network_isolation_real():
-    with pytest.raises(subprocess.CalledProcessError) as e:
+    with pytest.raises(external_commands.NetworkIsolationError) as e:
         external_commands.run(
             ["host", "github.com"],
             network_isolation=True,
             extra_environ={"LC_ALL": "C"},
         )
     exc = typing.cast(subprocess.CalledProcessError, e.value)
     assert exc.returncode == 1
-    assert "network unreachable" in exc.stdout