refactor: port all sys.exit over to kas exceptions

This patch replaces all direct invocations of sys.exit outside of the
main invocation to KasUserError based exceptions. By that, only one
method for returning is used and return codes can be handled
consistently. In addition, this makes it possible to handle specific
errors differently.

Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/libkas.py

@@ -34,11 +34,36 @@ import pathlib
 import signal
 from subprocess import Popen, PIPE
 from .context import get_context
+from .kasusererror import KasUserError, CommandExecError
 
 __license__ = 'MIT'
 __copyright__ = 'Copyright (c) Siemens AG, 2017-2018'
 
 
+class InitBuildEnvError(KasUserError):
+    """
+    Error related to the OE / ISAR environment setup scripts
+    """
+    pass
+
+
+class EnvNotValidError(KasUserError):
+    """
+    The caller environment is not suited for the requested operation
+    """
+    pass
+
+
+class TaskExecError(KasUserError):
+    """
+    Similar to :class:`kas.kasusererror.CommandExecError` but for kas
+    internal tasks
+    """
+    def __init__(self, command, ret_code):
+        self.ret_code = ret_code
+        super().__init__('{} failed: error code {}'.format(command, ret_code))
+
+
 class LogOutput:
     """
         Handles the log output of executed applications
@@ -144,7 +169,7 @@ def run_cmd(cmd, cwd, env=None, fail=True, liveupdate=True):
     (ret, output) = loop.run_until_complete(
         run_cmd_async(cmd, cwd, env, fail, liveupdate))
     if ret and fail:
-        sys.exit(ret)
+        raise CommandExecError(cmd, ret)
     return (ret, output)
 
 
@@ -175,7 +200,7 @@ def repos_fetch(repos):
 
     for task in tasks:
         if task.result():
-            sys.exit(task.result())
+            raise TaskExecError('fetch repos', task.result())
 
 
 def repos_apply_patches(repos):
@@ -194,7 +219,7 @@ def repos_apply_patches(repos):
 
     for task in tasks:
         if task.result():
-            sys.exit(task.result())
+            raise TaskExecError('apply patches', task.result())
 
 
 def get_build_environ(build_system):
@@ -217,15 +242,15 @@ def get_build_environ(build_system):
     for (repo, script) in permutations:
         if os.path.exists(repo.path + '/' + script):
             if init_repo:
-                logging.error('Multiple init scripts found (%s vs. %s). ',
-                              repo.name, init_repo.name)
-                logging.error('Resolve ambiguity by removing one of the repos')
-                sys.exit(1)
+                raise InitBuildEnvError(
+                    'Multiple init scripts found ({} vs. {}). '
+                    'Resolve ambiguity by removing one of the repos'
+                    .format(repo.name, init_repo.name))
+
             init_repo = repo
             init_script = script
     if not init_repo:
-        logging.error('Did not find any init-build-env script')
-        sys.exit(1)
+        raise InitBuildEnvError('Did not find any init-build-env script')
 
     with tempfile.TemporaryDirectory() as temp_dir:
         script = """#!/bin/bash
@@ -412,9 +437,8 @@ def run_handle_preserve_env_arg(ctx, os, args, SetupHome):
                                 var)
 
         if not os.isatty(sys.stdout.fileno()):
-            logging.error("Error: --preserve-env can only be "
-                          "run from a tty")
-            sys.exit(1)
+            raise EnvNotValidError(
+                '--preserve-env can only be run from a tty')
 
         ctx.environ = os.environ.copy()