update: Write certain errors to stderr

mypy/errors.py

@@ -374,8 +374,10 @@ def report_internal_error(err: Exception, file: str, line: int) -> None:
     for s in traceback.format_list(tb + tb2):
         print(s.rstrip('\n'))
     print('{}: {}'.format(type(err).__name__, err))
-    print('\n*** INTERNAL ERROR ***')
+    print('\n*** INTERNAL ERROR ***', file=sys.stderr)
     print('\n{}:{}: error: Internal error --'.format(file, line),
-          'please report a bug at https://github.com/JukkaL/mypy/issues')
-    print('\nNOTE: you can use "mypy --pdb ..." to drop into the debugger when this happens.')
+          'please report a bug at https://github.com/JukkaL/mypy/issues',
+          file=sys.stderr)
+    print('\nNOTE: you can use "mypy --pdb ..." to drop into the debugger when this happens.',
+          file=sys.stderr)
     sys.exit(1)

mypy/lex.py

@@ -880,7 +880,7 @@ def ignore_break(self) -> bool:
     # Lexically analyze a file and dump the tokens to stdout.
     import sys
     if len(sys.argv) != 2:
-        print('Usage: lex.py FILE')
+        print('Usage: lex.py FILE', file=sys.stderr)
         sys.exit(2)
     fnam = sys.argv[1]
     s = open(fnam, 'rb').read()

mypy/main.py

@@ -56,7 +56,7 @@ def main(script_path: str) -> None:
             raise RuntimeError('unsupported target %d' % options.target)
     except CompileError as e:
         for m in e.messages:
-            sys.stdout.write(m + '\n')
+            sys.stderr.write(m + '\n')
         sys.exit(1)
 
 

mypy/parse.py

@@ -1978,7 +1978,7 @@ def token_repr(tok: Token) -> str:
     import sys
 
     def usage():
-        print('Usage: parse.py [--py2] [--quiet] FILE [...]')
+        print('Usage: parse.py [--py2] [--quiet] FILE [...]', file=sys.stderr)
         sys.exit(2)
 
     args = sys.argv[1:]

mypy/stubgen.py

@@ -148,7 +148,7 @@ def load_python_module_info(module: str, interpreter: str) -> Tuple[str, Optiona
     try:
         output_bytes = subprocess.check_output(cmd_template % code, shell=True)
     except subprocess.CalledProcessError:
-        print("Can't import module %s" % module)
+        print("Can't import module %s" % module, file=sys.stderr)
         sys.exit(1)
     output = output_bytes.decode('ascii').strip().splitlines()
     module_path = output[0]