fix: Hide stacktrace on resolution failure

Author: brandonchinn178

CHANGELOG.md

@@ -102,6 +102,7 @@ Unreleased changes template.
 * (packaging) An empty `requires_file` is treated as if it were omitted, resulting in a valid `METADATA` file.
 * (rules) py_wheel and sphinxdocs rules now propagate `target_compatible_with` to all targets they create.
   [PR #2788](https://github.com/bazel-contrib/rules_python/pull/2788).
+* (pypi) Dependency resolution failures no longer show the full exception traceback in the output
 
 {#v0-0-0-added}
 ### Added

python/private/pypi/dependency_resolver/dependency_resolver.py

@@ -24,6 +24,8 @@
 
 import click
 import piptools.writer as piptools_writer
+from pip._internal.exceptions import DistributionNotFound
+from pip._vendor.resolvelib.resolvers import ResolutionImpossible
 from piptools.scripts.compile import cli
 
 from python.runfiles import runfiles
@@ -201,6 +203,7 @@ def main(
         requirements_file_relative_path.write_text(content)
     else:
         print("Checking " + requirements_file)
+        sys.stdout.flush()
         _run_pip_compile()
         golden = open(_locate(bazel_runfiles, requirements_file)).readlines()
         out = open(requirements_out).readlines()
@@ -223,6 +226,14 @@ def run_pip_compile(
 ) -> None:
     try:
         cli(args, standalone_mode=False)
+    except DistributionNotFound as e:
+        if isinstance(e.__cause__, ResolutionImpossible):
+            # pip logs an informative error to stderr already
+            # just render the error and exit
+            print(e)
+            sys.exit(1)
+        else:
+            raise
     except SystemExit as e:
         if e.code == 0:
             return  # shouldn't happen, but just in case