cli: add spinning wheel for vulnerability list

Add a spinning wheel when users are running the pro vulnerability list
command. This should better inform users that some processing is
happening in the background

features/cli/vulnerability_list.feature

@@ -23,7 +23,7 @@ Feature: CLI vulnerability list command
     And I run `pro vulnerability list --data-file=/tmp/security_issues_xenial.json --manifest-file=/tmp/manifest` as non-root
     And I remove colors from output
     And I remove links from output
-    Then I will see the following on stdout:
+    Then stdout contains substring:
       """
       Common vulnerabilities and exposures (CVE):
       VULNERABILITY     PRIORITY    FIX AVAILABLE FROM  AFFECTED INSTALLED PACKAGES
@@ -47,7 +47,7 @@ Feature: CLI vulnerability list command
     When I run `pro vulnerability list --all --data-file=/tmp/security_issues_xenial.json --manifest-file=/tmp/manifest` as non-root
     And I remove colors from output
     And I remove links from output
-    Then I will see the following on stdout:
+    Then stdout contains substring:
       """
       Common vulnerabilities and exposures (CVE):
       VULNERABILITY     PRIORITY    FIX AVAILABLE FROM  AFFECTED INSTALLED PACKAGES
@@ -83,7 +83,7 @@ Feature: CLI vulnerability list command
     When I run `pro vulnerability list --unfixable --data-file=/tmp/security_issues_xenial.json --manifest-file=/tmp/manifest` as non-root
     And I remove colors from output
     And I remove links from output
-    Then I will see the following on stdout:
+    Then stdout contains substring:
       """
       Common vulnerabilities and exposures (CVE):
       VULNERABILITY   PRIORITY  FIX AVAILABLE FROM  AFFECTED INSTALLED PACKAGES
@@ -106,7 +106,7 @@ Feature: CLI vulnerability list command
     When I run `pro vulnerability list --usns --data-file=/tmp/security_issues_xenial.json --manifest-file=/tmp/manifest` as non-root
     And I remove colors from output
     And I remove links from output
-    Then I will see the following on stdout:
+    Then stdout contains substring:
       """
       Ubuntu Security Notices (USN):
       VULNERABILITY  FIX AVAILABLE FROM  AFFECTED INSTALLED PACKAGES
@@ -128,13 +128,13 @@ Feature: CLI vulnerability list command
       """
     When I run `pro vulnerability list --data-file=/tmp/security_issues_xenial.json --manifest-file=/tmp/manifest` as non-root
     And I remove colors from output
-    Then I will see the following on stdout:
+    Then stdout contains substring:
       """
       No CVEs found that affects this system
       """
     When I run `pro vulnerability list --usns --data-file=/tmp/security_issues_xenial.json --manifest-file=/tmp/manifest` as non-root
     And I remove colors from output
-    Then I will see the following on stdout:
+    Then stdout contains substring:
       """
       No USNs found that affects this system
       """

uaclient/cli/vulnerability/list.py

@@ -1,4 +1,8 @@
+import itertools
 import re
+import sys
+import threading
+import time
 from typing import Any, Dict  # noqa: F401
 
 from uaclient import config, exceptions, messages
@@ -363,6 +367,52 @@ def _create_list_header(
     return msg
 
 
+def run_spinner(stop_spinner):
+    spinner = itertools.cycle(["|", "/", "-", "\\"])
+    while not stop_spinner.is_set():
+        sys.stdout.write(next(spinner))
+        sys.stdout.flush()
+        time.sleep(0.1)
+        sys.stdout.write("\b")
+
+
+def _get_vulnerability_data_with_spinner(
+    cfg: config.UAConfig,
+    options,
+    get_vuln_func,
+):
+    print(messages.CLI_VULNERABILITY_LIST_SPINNER_MSG)
+    if not sys.stdout.isatty():
+        return get_vuln_func(
+            options=options,
+            cfg=cfg,
+        )
+
+    stop_spinner = threading.Event()
+
+    spinner_thread = threading.Thread(target=run_spinner, args=(stop_spinner,))
+    spinner_thread.start()
+
+    vulnerabilities_result, applied_fixes_count = get_vuln_func(
+        options=options,
+        cfg=cfg,
+    )
+
+    stop_spinner.set()
+    spinner_thread.join()
+    sys.stdout.write("\b")
+
+    return vulnerabilities_result, applied_fixes_count
+
+
+def _get_cve_data(cfg: config.UAConfig, cve_options):
+    return _get_vulnerability_data_with_spinner(
+        cfg=cfg,
+        options=cve_options,
+        get_vuln_func=cve_vulnerabilities,
+    )
+
+
 def _list_cves(
     cfg: config.UAConfig,
     show_all: bool,
@@ -371,15 +421,16 @@ def _list_cves(
     manifest_file: str,
     series: str,
 ):
-    cve_vulnerabilities_result, applied_fixes_count = cve_vulnerabilities(
-        options=CVEVulnerabilitiesOptions(
-            all=show_all,
-            unfixable=show_unfixable,
-            data_file=data_file,
-            manifest_file=manifest_file,
-            series=series,
-        ),
+    cve_options = CVEVulnerabilitiesOptions(
+        all=show_all,
+        unfixable=show_unfixable,
+        data_file=data_file,
+        manifest_file=manifest_file,
+        series=series,
+    )
+    cve_vulnerabilities_result, applied_fixes_count = _get_cve_data(
         cfg=cfg,
+        cve_options=cve_options,
     )
 
     if cve_vulnerabilities_result.cves:
@@ -402,6 +453,14 @@ def _list_cves(
         print(_create_already_fixed_cves_count(applied_fixes_count))
 
 
+def _get_usn_data(cfg: config.UAConfig, usn_options):
+    return _get_vulnerability_data_with_spinner(
+        cfg=cfg,
+        options=usn_options,
+        get_vuln_func=usn_vulnerabilities,
+    )
+
+
 def _list_usns(
     cfg: config.UAConfig,
     show_all: bool,
@@ -410,15 +469,16 @@ def _list_usns(
     manifest_file: str,
     series: str,
 ):
-    usn_vulnerabilities_result, applied_fixes_count = usn_vulnerabilities(
-        options=USNVulnerabilitiesOptions(
-            all=show_all,
-            unfixable=show_unfixable,
-            data_file=data_file,
-            manifest_file=manifest_file,
-            series=series,
-        ),
+    usn_options = USNVulnerabilitiesOptions(
+        all=show_all,
+        unfixable=show_unfixable,
+        data_file=data_file,
+        manifest_file=manifest_file,
+        series=series,
+    )
+    usn_vulnerabilities_result, applied_fixes_count = _get_usn_data(
         cfg=cfg,
+        usn_options=usn_options,
     )
 
     if usn_vulnerabilities_result.usns:

uaclient/messages/__init__.py

@@ -1308,6 +1308,10 @@ class TxtColor:
 By default, the command will only list CVEs. To display
 USNs instead, run the command with the --usns flag."""
 )
+CLI_VULNERABILITY_LIST_SPINNER_MSG = t.gettext(
+    """\
+Processing vulnerability data..."""
+)
 CLI_VULNERABILITY_LIST_CVE_HEADER = (
     TxtColor.DISABLEGREY
     + t.gettext("Common vulnerabilities and exposures (CVE):")