Add stdout/stderr to doctor calledProcesserror

Summary:
Doctor uses subproccesses to run many external commands

When these commands fail, we currently only get the error code, not the stdout/stderr
https://fb.workplace.com/groups/eden.users/permalink/8868413416541861/

This diff adds that output to the doctor log to assist in debugging

Reviewed By: genevievehelsel

Differential Revision: D67551014

fbshipit-source-id: f64c47094ef84816f5c6ae643f444e5a62402be0

eden/fs/cli/doctor/test/corrupt_hg_test.py

@@ -228,9 +228,19 @@ def patched_func() -> typing.List[str]:
 Found inconsistent/missing data in {hg_dot_path}:
   Found a journal file in backing repo, might have an interrupted transaction
 Repairing hg directory contents for {checkout_path}...<red>error<reset>
-(.*\n)+
+Failed to fix or verify fix for problem HgDirectoryError: CalledProcessError: Command 'hg' returned non-zero exit status 1.
+│ Traceback .*
+(.*\n){{15}}.*
+│ subprocess.CalledProcessError: Command 'hg' returned non-zero exit status 1.
+stdout:
+
+stderr:
+repair error
+
+
 <red>Failed to fix 1 problem.<reset>
 .*""",
+                msg=f"formatted output:\n{out.getvalue()}",
             )
 
     def _verify_hg_dir(self) -> None:

eden/fs/cli/doctor/util.py

@@ -169,6 +169,13 @@ def format_exception(ex: BaseException, with_tb: bool = False) -> str:
     result.append(f"{type(ex).__name__}: {ex}")
     if with_tb:
         result.extend(format_traceback(ex, "│ "))
+    # Get CalledProcess output
+    if type(ex) is subprocess.CalledProcessError:
+        result.append("stdout:")
+        result.append(ex.stdout.decode("utf-8"))
+        result.append("stderr:")
+        result.append(ex.stderr.decode("utf-8"))
+
     context = ex.__context__
 
     if context: