[lldbsuite] Fix the filecheck functionality to work with Python 3

[stella.stamenova]

Summary

This is another string/byte conversion issue between Python 2 and 3. In Python 2, the subprocess communication expects a byte string, but in Python 3, it expects bytes. Since both versions are capable of using strings when universal_newlines is set to True AND filecheck operates on strings, force the use of strings.

[zturner]

packages/Python/lldbsuite/test/lldbtest.py

2230–2233

Ok I had to stare at this for a long time to figure out what was going on. I think you need to update the comment here, because it makes it sounds like output is the result of a Popen.communicate. But output is the result of a debugger.HandleCommand().

I think we should actually just leave this the way it was and fix it in the call to Popen (see below)

2243–2245

If I'm not mistaken, Python 3 can accept stdin as bytes or string, and either will work, it depends on the value of universal_newlines, and stdout will be in whatever format stdin was in. If we pass universal_newlines=True, then it will expect a string and output a string, otherwise it expects a bytes and output a bytes. Given that FileCheck is supposed to operate on textual data and not binary data, perhaps we should be doing that here?

[stella.stamenova]

Force the comparison in filecheck to use text rather than bytes

packages/Python/lldbsuite/test/lldbtest.py

2243–2245

Brilliant! :)

packages/Python/lldbsuite/test/lldbtest.py

def filecheck(
         # Run the command.
         self.runCmd(
                 command,
                 msg="FileCheck'ing result of `{0}`".format(command))
 
         # Get the error text if there was an error, and the regular text if not.
         output = self.res.GetOutput() if self.res.Succeeded() \
                 else self.res.GetError()
 
         # Assemble the absolute path to the check file. As a convenience for
         # LLDB inline tests, assume that the check file is a relative path to
         # a file within the inline test directory.
         if check_file.endswith('.pyc'):
             check_file = check_file[:-1]
         check_file_abs = os.path.abspath(check_file)
 
         # Run FileCheck.
         filecheck_bin = configuration.get_filecheck_path()
         filecheck_args = [filecheck_bin, check_file_abs]
         if filecheck_options:
             filecheck_args.append(filecheck_options)
-        subproc = Popen(filecheck_args, stdin=PIPE, stdout=PIPE, stderr=PIPE)
+        subproc = Popen(filecheck_args, stdin=PIPE, stdout=PIPE, stderr=PIPE, universal_newlines = True)
         cmd_stdout, cmd_stderr = subproc.communicate(input=output)
         cmd_status = subproc.returncode
 
         filecheck_cmd = " ".join(filecheck_args)
         filecheck_trace = """
 --- FileCheck trace (code={0}) ---
 {1}
 
 FileCheck input:
 {2}