Fix-6911(pytest-bot): Added error from commands that are run

Earlier pytest-bot would only print out the exception in cases of
failure but did not provide context on failing command and error from
command. This patch adds the errors from the command to the exception
message.
`Command` provides abstraction over the command to run and helps
in collecting errors from the first failing command only.
With this, we don't need to check `returncode` from each command that
we run, we can run all the commands and will have access to the error
from the first command that failed. This pattern was taken from Go.
Please refer: https://blog.golang.org/errors-are-values

scripts/release-on-comment.py

@@ -33,6 +33,9 @@ import sys
 from pathlib import Path
 from subprocess import check_call
 from subprocess import check_output
+from subprocess import PIPE
+from subprocess import run
+from subprocess import STDOUT
 from textwrap import dedent
 from typing import Dict
 from typing import Optional
@@ -91,6 +94,7 @@ def print_and_exit(msg) -> None:
 
 
 def trigger_release(payload_path: Path, token: str) -> None:
+    error_contents = ""  # to be used to store error output in case any command fails
     payload, base_branch = validate_and_get_issue_comment_payload(payload_path)
     if base_branch is None:
         url = get_comment_data(payload)["html_url"]
@@ -119,19 +123,42 @@ def trigger_release(payload_path: Path, token: str) -> None:
 
         release_branch = f"release-{version}"
 
-        check_call(["git", "config", "user.name", "pytest bot"])
-        check_call(["git", "config", "user.email", "pytestbot@gmail.com"])
+        run(
+            ["git", "config", "user.name", "pytest bot"],
+            text=True,
+            check=True,
+            capture_output=True,
+        )
+        run(
+            ["git", "config", "user.email", "pytestbot@gmail.com"],
+            text=True,
+            check=True,
+            capture_output=True,
+        )
 
-        check_call(["git", "checkout", "-b", release_branch, f"origin/{base_branch}"])
+        run(
+            ["git", "checkout", "-b", release_branch, f"origin/{base_branch}"],
+            text=True,
+            check=True,
+            capture_output=True,
+        )
 
         print(f"Branch {Fore.CYAN}{release_branch}{Fore.RESET} created.")
 
-        check_call(
-            [sys.executable, "scripts/release.py", version, "--skip-check-links"]
+        run(
+            [sys.executable, "scripts/release.py", version, "--skip-check-links"],
+            text=True,
+            check=True,
+            capture_output=True,
         )
 
         oauth_url = f"https://{token}:x-oauth-basic@github.com/{SLUG}.git"
-        check_call(["git", "push", oauth_url, f"HEAD:{release_branch}", "--force"])
+        run(
+            ["git", "push", oauth_url, f"HEAD:{release_branch}", "--force"],
+            text=True,
+            check=True,
+            capture_output=True,
+        )
         print(f"Branch {Fore.CYAN}{release_branch}{Fore.RESET} pushed.")
 
         body = PR_BODY.format(
@@ -151,7 +178,10 @@ def trigger_release(payload_path: Path, token: str) -> None:
         print(f"Notified in original comment {Fore.CYAN}{comment.url}{Fore.RESET}.")
 
         print(f"{Fore.GREEN}Success.")
+    except CallProcessError as e:
+        error_contents = e.output
     except Exception as e:
+        error_contents = str(e)
         link = f"https://github.com/{SLUG}/actions/runs/{os.environ['GITHUB_RUN_ID']}"
         issue.create_comment(
             dedent(
@@ -168,6 +198,23 @@ def trigger_release(payload_path: Path, token: str) -> None:
         )
         print_and_exit(f"{Fore.RED}{e}")
 
+    if error_contents:
+        link = f"https://github.com/{SLUG}/actions/runs/{os.environ['GITHUB_RUN_ID']}"
+        issue.create_comment(
+            dedent(
+                f"""
+                Sorry, the request to prepare release `{version}` from {base_branch} failed with:
+
+                ```
+                {error_contents}
+                ```
+
+                See: {link}.
+                """
+            )
+        )
+        print_and_exit(f"{Fore.RED}{e}")
+
 
 def find_next_version(base_branch: str) -> str:
     output = check_output(["git", "tag"], encoding="UTF-8")