scripts: Print errors to stderr instead of stdout

doc/changelog.asciidoc

@@ -62,6 +62,8 @@ Fixed
   when using `:spawn --userscript`.
 - `:version` and `--version` now don't crash if there's an (invalid)
   `/etc/os-release` file which has non-comment lines without a `=` character.
+- Scripts in `scripts/` now report errors to `stderr` correctly, instead of
+  using `stdout`.
 
 v1.10.2 (2020-04-17)
 --------------------

scripts/asciidoc2html.py

@@ -263,8 +263,9 @@ class AsciiDoc:
             subprocess.run(cmdline, check=True, env=env)
         except (subprocess.CalledProcessError, OSError) as e:
             self._failed = True
-            utils.print_col(str(e), 'red')
-            print("Keeping modified sources in {}.".format(self._homedir))
+            utils.print_error(str(e))
+            print("Keeping modified sources in {}.".format(self._homedir),
+                  file=sys.stderr)
             sys.exit(1)
 
 
@@ -291,9 +292,9 @@ def run(**kwargs):
     try:
         asciidoc.prepare()
     except FileNotFoundError:
-        utils.print_col("Could not find asciidoc! Please install it, or use "
-                        "the --asciidoc argument to point this script to the "
-                        "correct python/asciidoc.py location!", 'red')
+        utils.print_error("Could not find asciidoc! Please install it, or use "
+                          "the --asciidoc argument to point this script to "
+                          "the correct python/asciidoc.py location!")
         sys.exit(1)
 
     try:

scripts/dev/build_release.py

@@ -423,8 +423,8 @@ def github_upload(artifacts, tag):
                 with open(filename, 'rb') as f:
                     release.upload_asset(mimetype, basename, f, description)
             except github3.exceptions.ConnectionError as e:
-                utils.print_col('Failed to upload: {}'.format(e), 'red')
-                print("Press Enter to retry...")
+                utils.print_error('Failed to upload: {}'.format(e))
+                print("Press Enter to retry...", file=sys.stderr)
                 input()
                 print("Retrying!")
 

scripts/dictcli.py

@@ -225,7 +225,7 @@ def install(languages):
                    "system-wide. If your qutebrowser uses a newer Qt version "
                    "via a virtualenv, make sure you start this script with "
                    "the virtualenv's Python.".format(e))
-            scriptutils.print_col(msg, 'red')
+            scriptutils.print_error(msg)
             sys.exit(1)
 
 

scripts/mkvenv.py

@@ -101,7 +101,7 @@ def run_venv(venv_dir: pathlib.Path, executable, *args: str) -> None:
         subprocess.run([str(venv_dir / subdir / executable)] +
                        [str(arg) for arg in args], check=True)
     except subprocess.CalledProcessError as e:
-        utils.print_col("Subprocess failed, exiting", 'red')
+        utils.print_error("Subprocess failed, exiting")
         sys.exit(e.returncode)
 
 
@@ -124,9 +124,9 @@ def show_tox_error(pyqt_type: str) -> None:
         raise AssertionError
 
     print()
-    utils.print_col('tox -e {} is deprecated. '
-                    'Please use "python3 scripts/mkvenv.py{}" instead.'
-                    .format(env, args), 'red')
+    utils.print_error('tox -e {} is deprecated. '
+                      'Please use "python3 scripts/mkvenv.py{}" instead.'
+                      .format(env, args))
     print()
 
 
@@ -143,9 +143,8 @@ def delete_old_venv(venv_dir: pathlib.Path) -> None:
     ]
 
     if not any(m.exists() for m in markers):
-        utils.print_col('{} does not look like a virtualenv, '
-                        'cowardly refusing to remove it.'.format(venv_dir),
-                        'red')
+        utils.print_error('{} does not look like a virtualenv, '
+                          'cowardly refusing to remove it.'.format(venv_dir))
         sys.exit(1)
 
     utils.print_col('$ rm -r {}'.format(venv_dir), 'blue')
@@ -160,7 +159,7 @@ def create_venv(venv_dir: pathlib.Path, use_virtualenv: bool = False) -> None:
             subprocess.run([sys.executable, '-m', 'virtualenv', venv_dir],
                            check=True)
         except subprocess.CalledProcessError as e:
-            utils.print_col("virtualenv failed, exiting", 'red')
+            utils.print_error("virtualenv failed, exiting")
             sys.exit(e.returncode)
     else:
         utils.print_col('$ python3 -m venv {}'.format(venv_dir), 'blue')
@@ -269,12 +268,12 @@ def main() -> None:
         sys.exit(1)
     elif (args.pyqt_version != 'auto' and
           args.pyqt_type not in ['binary', 'source']):
-        utils.print_col('The --pyqt-version option is only available when '
-                        'installing PyQt from binary or source', 'red')
+        utils.print_error('The --pyqt-version option is only available when '
+                          'installing PyQt from binary or source')
         sys.exit(1)
     elif args.pyqt_wheels_dir != 'wheels' and args.pyqt_type != 'wheels':
-        utils.print_col('The --pyqt-wheels-dir option is only available when '
-                        'installing PyQt from wheels', 'red')
+        utils.print_error('The --pyqt-wheels-dir option is only available '
+                          'when installing PyQt from wheels')
         sys.exit(1)
 
     if not args.keep:

scripts/utils.py

@@ -21,6 +21,7 @@
 
 import os
 import os.path
+import sys
 
 
 # Import side-effects are an evil thing, but here it's okay so scripts using
@@ -58,14 +59,18 @@ def _esc(code):
     return '\033[{}m'.format(code)
 
 
-def print_col(text, color):
+def print_col(text, color, file=sys.stdout):
     """Print a colorized text."""
     if use_color:
         fg = _esc(fg_colors[color.lower()])
         reset = _esc(fg_colors['reset'])
-        print(''.join([fg, text, reset]))
+        print(''.join([fg, text, reset]), file=file)
     else:
-        print(text)
+        print(text, file=file)
+
+
+def print_error(text):
+    print_col(text, 'red', file=sys.stderr)
 
 
 def print_title(text):