Use awscli python instead of calling subprocess. Fixes issue with PAT…

…H in Jupyter. Also add docstring

cosipy/util/data_fetching.py

@@ -1,23 +1,46 @@
-import subprocess, os
+import os
+from awscli.clidriver import create_clidriver
 
 def fetch_wasabi_file(file,
                       output = None,
                       override = False,
                       bucket = 'cosi-pipeline-public',
                       endpoint = 'https://s3.us-west-1.wasabisys.com',
-                      access_key_id = 'GBAL6XATQZNRV3GFH9Y4',
-                      access_key = 'GToOczY5hGX3sketNO2fUwiq4DJoewzIgvTCHoOv'):
+                      access_key = 'GBAL6XATQZNRV3GFH9Y4',
+                      secret_key = 'GToOczY5hGX3sketNO2fUwiq4DJoewzIgvTCHoOv'):
+    """
+    Download a file from COSI's Wasabi acccount.
 
+    Parameters
+    ----------
+    file: str
+        Full path to file in Wasabi
+    output: str
+        Full path to the downloaded file in the local system. By default it will use 
+        the current durectory and the same file name as the input file.
+    bucket: str
+        Passed to aws --bucket option
+    endpoint: str:
+        Passed to aws --endpoint-url option
+    access_key: str
+        AWS_ACCESS_KEY_ID
+    secret_key: str
+        AWS_SECRET_ACCESS_KEY
+    """
+
     if output is None:
         output = file.split('/')[-1]
 
     if os.path.exists(output) and not override:
         raise RuntimeError(f"File {output} already exists.")
-
-    subprocess.run(['aws', 's3api', 'get-object',
-                    '--bucket', bucket,
-                    '--key', file,
-                    '--endpoint-url', endpoint,
-                    output], 
-                   env = os.environ.copy() | {'AWS_ACCESS_KEY_ID':access_key_id,
-                                              'AWS_SECRET_ACCESS_KEY':access_key})
+
+    cli = create_clidriver()
+
+    cli.session.set_credentials(access_key, secret_key)
+
+    cli.main(['s3api', 'get-object',
+              '--bucket', bucket,
+              '--key', file,
+              '--endpoint-url', endpoint,
+              output])
+