fix vendor pull error message (#940)

* fix vendor pull error message

* Added more error handling messages

* fix test case

internal/exec/vendor_utils.go

@@ -181,7 +181,16 @@ func ReadAndProcessVendorConfigFile(
 	// Check if it's a directory
 	fileInfo, err := os.Stat(foundVendorConfigFile)
 	if err != nil {
-		return vendorConfig, false, "", err
+		if os.IsNotExist(err) {
+			// File does not exist
+			return vendorConfig, false, "", fmt.Errorf("Vendoring is not configured. To set up vendoring, please see https://atmos.tools/core-concepts/vendor/")
+		}
+		if os.IsPermission(err) {
+			// Permission error
+			return vendorConfig, false, "", fmt.Errorf("Permission denied when accessing '%s'. Please check the file permissions.", foundVendorConfigFile)
+		}
+		// Other errors
+		return vendorConfig, false, "", fmt.Errorf("An error occurred while accessing the vendoring configuration: %w", err)
 	}
 
 	var configFiles []string

tests/test-cases/vendor-test.yaml

@@ -0,0 +1,13 @@
+tests:
+  - name: atmos vendor pull
+    enabled: true
+    description: ""
+    workdir: "../"
+    command: "atmos"
+    args:
+      - "vendor"
+      - "pull"
+    expect:
+      stderr:
+        - "Vendoring is not configured. To set up vendoring, please see https://atmos.tools/core-concepts/vendor/"
+      exit_code: 1