Eval / execute: Raise a ShellCommandError if command is not available

src/fsh.nim

@@ -274,9 +274,14 @@ proc execute(cmd: string): int =
       stdout.write(runBuiltin(progname, args))
       result = 0
       continue
-    let ps = startProcess(progname, args=args, options={poUsePath, poParentStreams})
-    result =  ps.waitForExit
-    ps.close
+    try:
+      let ps = startProcess(progname, args=args, options={poUsePath, poParentStreams})
+      result =  ps.waitForExit
+      ps.close
+    except OSError as e:
+      var e = newException(ShellCommandError, progname & ": command not found")
+      e.command = progname
+      raise e
   strm.close
 
 # eval evaluates the given string
@@ -291,9 +296,14 @@ proc eval(cmd: string): string =
     if progname in builtins:
       result = runBuiltin(progname, args)
       continue
-    let ps = startProcess(progname, args=args, options={poUsePath})
-    result=ps.outputStream.readAll
-    ps.close
+    try:
+      let ps = startProcess(progname, args=args, options={poUsePath})
+      result=ps.outputStream.readAll
+      ps.close
+    except OSError as e:
+      var e = newException(ShellCommandError, progname & ": Command not found")
+      e.command=progname
+      raise e
   strm.close
 
 when isMainModule: