From 39022139ae2ae5a44a41496d5db20069655aae34 Mon Sep 17 00:00:00 2001
From: jennypng <63012604+JennyPng@users.noreply.github.com>
Date: Mon, 18 May 2026 14:32:06 -0700
Subject: [PATCH 1/2] output doc link for 401 error

---
 .../eng/scripts/setup/package_manager.py         | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/packages/http-client-python/eng/scripts/setup/package_manager.py b/packages/http-client-python/eng/scripts/setup/package_manager.py
index 3b6698279d9..5725bddab35 100644
--- a/packages/http-client-python/eng/scripts/setup/package_manager.py
+++ b/packages/http-client-python/eng/scripts/setup/package_manager.py
@@ -100,10 +100,20 @@ def install_packages(packages: list, venv_context=None, package_manager: str = N
 
     try:
         if cwd:
-            subprocess.check_call(install_cmd + packages, cwd=cwd)
+            result = subprocess.run(install_cmd + packages, cwd=cwd, capture_output=True, text=True)
         else:
-            subprocess.check_call(install_cmd + packages)
-    except subprocess.CalledProcessError as e:
+            result = subprocess.run(install_cmd + packages, capture_output=True, text=True)
+        if result.returncode != 0:
+            error_output = (result.stderr or "") + (result.stdout or "")
+            error_msg = f"Failed to install packages with {package_manager}: command exited with code {result.returncode}\n{error_output}"
+            if "401" in error_output or "Unauthorized" in error_output:
+                error_msg += (
+                    "\n\nReceived a 401 Unauthorized error from the Azure feed. "
+                    "A pip dependency may not yet be cached. To fix this, follow the authentication steps at: "
+                    "https://github.com/Azure/azure-sdk-for-python/blob/main/CONTRIBUTING.md#authentication-for-upstream-pull-through"
+                )
+            raise RuntimeError(error_msg)
+    except OSError as e:
         raise RuntimeError(f"Failed to install packages with {package_manager}: {e}")
 
 

From 62fb7bb5809d5f7b1969329403431c8ec73a3042 Mon Sep 17 00:00:00 2001
From: jennypng <63012604+JennyPng@users.noreply.github.com>
Date: Mon, 18 May 2026 15:08:45 -0700
Subject: [PATCH 2/2] chronus

---
 .chronus/changes/cfs-error-message-2026-4-18-15-8-34.md | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 .chronus/changes/cfs-error-message-2026-4-18-15-8-34.md

diff --git a/.chronus/changes/cfs-error-message-2026-4-18-15-8-34.md b/.chronus/changes/cfs-error-message-2026-4-18-15-8-34.md
new file mode 100644
index 00000000000..80cc0766129
--- /dev/null
+++ b/.chronus/changes/cfs-error-message-2026-4-18-15-8-34.md
@@ -0,0 +1,7 @@
+---
+changeKind: internal
+packages:
+  - "@typespec/http-client-python"
+---
+
+When python emitter install fails due to 401 error, output informative instructions linking to resolution steps in the Python SDK's repo docs. 
\ No newline at end of file