test(changelog): fixes logic issue made evident by latest fix(git) commit

Exception is raised by git error: "fatal: your current branch 'master' does not have any commits yet". This response is more informative than the original "No commits found" exception and the "fail fast" logic is a bit easier to follow.

Author: bhelgs

tests/commands/test_changelog_command.py

@@ -6,6 +6,7 @@
 from commitizen.commands.changelog import Changelog
 from commitizen.exceptions import (
     DryRunExit,
+    GitCommandError,
     NoCommitsFoundError,
     NoRevisionError,
     NotAGitProjectError,
@@ -19,10 +20,12 @@ def test_changelog_on_empty_project(mocker):
     testargs = ["cz", "changelog", "--dry-run"]
     mocker.patch.object(sys, "argv", testargs)
 
-    with pytest.raises(NoCommitsFoundError) as excinfo:
+    with pytest.raises(GitCommandError):
         cli.main()
 
-    assert "No commits found" in str(excinfo)
+    #  git will error out with something like:
+    #  "your current branch 'XYZ' does not have any commits yet"
+    #  is it wise to assert the exception contains a message like this?
 
 
 @pytest.mark.usefixtures("tmp_commitizen_project")