build.lib.util, build.App: Beautify exceptions

Make exceptions somewhat more readable.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/build/App.py

@@ -458,4 +458,9 @@ class App(object):
         subparser = argparse.ArgumentParser(description=cmd_name)
         cmd.add_arguments(subparser)
         args = subparser.parse_args(sys.argv[(len(self.global_args) + 1)::])
-        return cmd.run(args)
+        try:
+            return cmd.run(args)
+        except Exception as e:
+            self.err('Failed to run >{}<: {}'.format(' '.join(sys.argv), e))
+            raise
+            sys.exit(1)

src/python/jw/build/lib/util.py

@@ -4,19 +4,22 @@ import os, sys, subprocess, json, time
 from argparse import Namespace
 from urllib.parse import urlparse
 
-def run_cmd(cmd: list[str], wd=None, throw=True, verbose=False) -> str|None: # export
-
+def pretty_cmd(cmd: list[str], wd=None):
     tokens = [cmd[0]]
     for token in cmd[1:]:
         if token.find(' ') != -1:
             token = '"' + token + '"'
         tokens.append(token)
-    subject = ' '.join(tokens)
+    ret = ' '.join(tokens)
     if wd is not None:
-        subject += f' in {wd}'
+        ret += f' in {wd}'
+    return ret
+
+def run_cmd(cmd: list[str], wd=None, throw=True, verbose=False) -> str|None: # export
+
     if verbose:
         delim_len = 120
-        delim = f'---- running {subject} -'
+        delim = f'---- running {pretty_cmd(cmd, wd)} -'
         delim = delim + '-' * (delim_len - len(delim))
         print(',' + delim + ' >')
 
@@ -37,7 +40,7 @@ def run_cmd(cmd: list[str], wd=None, throw=True, verbose=False) -> str|None: # e
         if p.returncode:
             if verbose:
                 print(' '.join(cmd) + ' failed')
-            raise Exception(time.strftime('%Y-%m-%d %H:%M') + f': failed to run "{subject}"')
+            raise Exception(time.strftime('%Y-%m-%d %H:%M') + f': Command returned an error: "{pretty_cmd(cmd, wd)}"')
     finally:
         if cwd:
             os.chdir(cwd)
@@ -50,7 +53,11 @@ def run_curl(args: list[str], parse_json: bool=True, wd=None, throw=None, verbos
     cmd.extend(args)
     ret = run_cmd(cmd, wd=wd, throw=throw, verbose=verbose)
     if parse_json:
-        return json.loads(ret)
+        try:
+            return json.loads(ret)
+        except Exception as e:
+            print(f'Failed to parse {len(ret)} bytes output of command >{pretty_cmd(cmd, wd)}< ({e})', file=sys.stderr)
+            raise
     return ret
 
 def get_username(args: Namespace|None=None, url: str|None=None) -> str: # export