Fix some error messages that printed directly to sys.stderr instead of logging

src/ocrmypdf/exec/tesseract.py

@@ -22,15 +22,7 @@ from collections import namedtuple
 from contextlib import suppress
 from functools import lru_cache
 from os import fspath
-from subprocess import (
-    PIPE,
-    STDOUT,
-    CalledProcessError,
-    TimeoutExpired,
-    check_output,
-    run,
-)
-from textwrap import dedent
+from subprocess import PIPE, STDOUT, CalledProcessError, TimeoutExpired, run
 
 from . import get_version
 from ..exceptions import (
@@ -88,8 +80,9 @@ def has_textonly_pdf(tesseract_env=None):
         )
         params = proc.stdout
     except CalledProcessError as e:
-        print("Could not --print-parameters from tesseract", file=sys.stderr)
-        raise MissingDependencyError from e
+        raise MissingDependencyError(
+            "Could not --print-parameters from tesseract"
+        ) from e
     if 'textonly_pdf' in params:
         return True
     return False
@@ -97,14 +90,13 @@ def has_textonly_pdf(tesseract_env=None):
 
 def languages(tesseract_env=None):
     def lang_error(output):
-        msg = dedent(
-            """Tesseract failed to report available languages.
-        Output from Tesseract:
-        -----------
-        """
+        msg = (
+            "Tesseract failed to report available languages.\n"
+            "Output from Tesseract:\n"
+            "-----------\n"
         )
         msg += output
-        print(msg, file=sys.stderr)
+        return msg
 
     args_tess = ['tesseract', '--list-langs']
     try:
@@ -118,13 +110,11 @@ def languages(tesseract_env=None):
         )
         output = proc.stdout
     except CalledProcessError as e:
-        lang_error(e.output)
-        raise MissingDependencyError from e
+        raise MissingDependencyError(lang_error(e.output)) from e
 
     header, *rest = output.splitlines()
     if not header.startswith('List of available languages'):
-        lang_error(output)
-        raise MissingDependencyError
+        raise MissingDependencyError(lang_error(output))
     return set(lang.strip() for lang in rest)
 
 

src/ocrmypdf/exec/unpaper.py

@@ -29,11 +29,7 @@ from tempfile import TemporaryDirectory
 from . import get_version
 from ..exceptions import MissingDependencyError, SubprocessOutputError
 
-try:
-    from PIL import Image
-except ImportError:
-    print("Could not find Python3 imaging library", file=sys.stderr)
-    raise
+from PIL import Image
 
 
 @lru_cache(maxsize=1)
@@ -55,16 +51,18 @@ def run(input_file, output_file, dpi, log, mode_args):
             else:
                 im = im.convert(mode='RGB')
         except IOError as e:
-            log.error("Could not convert image with type " + im.mode)
             im.close()
-            raise MissingDependencyError() from e
+            raise MissingDependencyError(
+                "Could not convert image with type " + im.mode
+            ) from e
 
     try:
         suffix = SUFFIXES[im.mode]
     except KeyError:
-        log.error("Failed to convert image to a supported format.")
         im.close()
-        raise MissingDependencyError() from e
+        raise MissingDependencyError(
+            "Failed to convert image to a supported format."
+        ) from e
 
     with TemporaryDirectory() as tmpdir:
         input_pnm = os.path.join(tmpdir, f'input{suffix}')

tests/conftest.py

@@ -37,8 +37,8 @@ else:
 # pylint: disable=E1101
 # pytest.helpers is dynamic so it confuses pylint
 
-if sys.version_info.major < 3:
-    print("Requires Python 3.4+")
+if sys.version_info < (3, 5):
+    print("Requires Python 3.5+")
     sys.exit(1)