Display the error message on one line if possible

src/codeql.test.ts

@@ -1189,8 +1189,8 @@ test("database finalize does not override no code found error on CodeQL 2.12.4",
       await codeqlObject.finalizeDatabase("db", "--threads=2", "--ram=2048"),
     {
       message:
-        'Encountered a fatal error while running "codeql-for-testing database finalize --finalize-dataset --threads=2 --ram=2048 db".\n' +
-        `Exit code was 32 and error was:\n${cliMessage}`,
+        'Encountered a fatal error while running "codeql-for-testing database finalize --finalize-dataset --threads=2 --ram=2048 db". ' +
+        `Exit code was 32 and error was: ${cliMessage}`,
     }
   );
 });

src/codeql.ts

@@ -54,9 +54,11 @@ export class CommandInvocationError extends Error {
     const prettyCommand = [cmd, ...args]
       .map((x) => (x.includes(" ") ? `'${x}'` : x))
       .join(" ");
+    error = error.trim();
+    const separator = error.includes("\n") ? "\n" : " ";
     super(
-      `Encountered a fatal error while running "${prettyCommand}".\n` +
-        `Exit code was ${exitCode} and error was:\n` +
+      `Encountered a fatal error while running "${prettyCommand}".${separator}` +
+        `Exit code was ${exitCode} and error was:${separator}` +
         `${error}`
     );
   }