[llvm] [lit] Add readfile substitution (PR #158441)

[Aiden Grossman via llvm-commits]

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@@ -729,8 +729,11 @@ def _replaceReadFile(match):
             filePath = match.group(1)
             if not os.path.isabs(filePath):
                 filePath = os.path.join(cwd, filePath)
-            with open(filePath) as fileHandle:
-                return fileHandle.read()
+            try:
+                with open(filePath) as fileHandle:
+                    return fileHandle.read()
+            except FileNotFoundError:
+                raise InternalShellError(cmd, "File does not exist: %s" % filePath)
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boomanaiden154 wrote:

Added a mention of readfile.

https://github.com/llvm/llvm-project/pull/158441