better processing for subcommands

Old versions cached full output to memory and only after that printed it
into log. This behaviour causes issues in case if operation stucks and
you would need to find the step at which it does. New check_output
method uses Popen directly and iterates over stdout lines

Also changed behaviour from merging stderr into stdout to separate
stderr logging.

Any other behaviour of the function must be the same.

Also changed GPG.key_import method to disable local signing since it
seems it is useless (and may break process in case if there is no
private key)

src/ahriman/core/util.py

@@ -27,7 +27,7 @@ import tempfile
 from contextlib import contextmanager
 from logging import Logger
 from pathlib import Path
-from typing import Any, Dict, Generator, Iterable, Optional, Union
+from typing import Any, Dict, Generator, Iterable, List, Optional, Union
 
 from ahriman.core.exceptions import InvalidOption, UnsafeRun
 from ahriman.models.repository_paths import RepositoryPaths
@@ -45,21 +45,39 @@ def check_output(*args: str, exception: Optional[Exception], cwd: Optional[Path]
     :param user: run process as specified user
     :return: command output
     """
-    try:
-        # universal_newlines is required to read input from string
-        # FIXME additional workaround for linter and type check which do not know that user arg is supported
-        # pylint: disable=unexpected-keyword-arg
-        result: str = subprocess.check_output(args, cwd=cwd, input=input_data, stderr=subprocess.STDOUT,
-                                              universal_newlines=True, user=user).strip()  # type: ignore
+    def log(single: str) -> None:
         if logger is not None:
-            for line in result.splitlines():
-                logger.debug(line)
-        return result
-    except subprocess.CalledProcessError as e:
-        if e.output is not None and logger is not None:
-            for line in e.output.splitlines():
-                logger.debug(line)
-        raise exception or e
+            logger.debug(single)
+
+    # FIXME additional workaround for linter and type check which do not know that user arg is supported
+    # pylint: disable=unexpected-keyword-arg
+    with subprocess.Popen(args, cwd=cwd, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                          user=user, text=True, encoding="utf8", bufsize=1) as process:  # type: ignore
+        if input_data is not None:
+            process.stdin.write(input_data)
+            process.stdin.close()
+
+        # read stdout and append to output result
+        result: List[str] = []
+        for line in iter(process.stdout.readline, ""):
+            line = line.strip()
+            if not line:  # skip empty lines
+                continue
+            result.append(line)
+            log(line)
+
+        # read stderr and write info to logs
+        for line in iter(process.stderr.readline, ""):
+            log(line.strip())
+
+        process.terminate()  # make sure that process is terminated
+        status_code = process.wait()
+        if status_code != 0:
+            if exception is not None:
+                raise exception
+            raise subprocess.CalledProcessError(status_code, process.args)
+
+        return "\n".join(result)
 
 
 def check_user(paths: RepositoryPaths, unsafe: bool) -> None: