Merge bitcoin/bitcoin#26212: contrib: Fix capture_output in getcoins.py

be59bd1 contrib: Fix capture_output in getcoins.py (willcl-ark)

Pull request description:

  Our minimum required Python version 3.6.12 does not support `capture_output` as a subprocess.run argument; this was added in python 3.7.

  We can emulate it by setting both stdout and stderr to `subprocess.PIPE`

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Tree-SHA512: 3158bfe657e2d5b263c9337a7ac1dd830e7e119854ec54a40a9e511329fe5bed073350bf70c66b5a6cc9a27dc8eb0e062bbac3969640fd7d6475379726003c98

Author: MacroFake

contrib/signet/getcoins.py

@@ -129,7 +129,7 @@ def bitcoin_cli(rpc_command_and_params):
 
     # Convert SVG image to PPM, and load it
     try:
-        rv = subprocess.run([args.imagemagick, 'svg:-', '-depth', '8', 'ppm:-'], input=res.content, check=True, capture_output=True)
+        rv = subprocess.run([args.imagemagick, 'svg:-', '-depth', '8', 'ppm:-'], input=res.content, check=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     except FileNotFoundError:
         raise SystemExit(f"The binary {args.imagemagick} could not be found. Please make sure ImageMagick (or a compatible fork) is installed and that the correct path is specified.")