Only output traceback if verbosity level > 2

[homebysix]

Resolves #608

[nmcspadden]

Same thing I always ask for:
Please show output demonstrating the change.

[homebysix]

Here's the verbose output before:

% autopkg run -vv EasyCrop.download.recipe
Processing EasyCrop.download.recipe...
WARNING: EasyCrop.download.recipe is missing trust info and FAIL_RECIPES_WITHOUT_TRUST_INFO is not set. Proceeding...
DeprecationWarning
{'Input': {}}
DeprecationWarning: ### This recipe has been deprecated. It may be removed soon. ###
{'Output': {'deprecation_summary_result': {'data': {'name': 'EasyCrop.download',
                                                    'warning': '### This '
                                                               'recipe has '
                                                               'been '
                                                               'deprecated. It '
                                                               'may be removed '
                                                               'soon. ###'},
                                           'report_fields': ['name', 'warning'],
                                           'summary_text': 'The following '
                                                           'recipes have '
                                                           'deprecation '
                                                           'warnings:'}}}
SparkleUpdateInfoProvider
{'Input': {'appcast_url': 'https://yellowmug.com/easycrop/appcast.xml'}}
SparkleUpdateInfoProvider: Version retrieved from appcast: 2.4.5
SparkleUpdateInfoProvider: Found URL http://yellowmug.com/download/EasyCrop_2.4.5.dmg
{'Output': {'url': 'http://yellowmug.com/download/EasyCrop_2.4.5.dmg',
            'version': '2.4.5'}}
URLDownloader
{'Input': {'filename': 'EasyCrop-2.4.5.dmg',
           'url': 'http://yellowmug.com/download/EasyCrop_2.4.5.dmg'}}
URLDownloader: No value supplied for prefetch_filename, setting default value of: False
URLDownloader: No value supplied for CHECK_FILESIZE_ONLY, setting default value of: False
Traceback (most recent call last):
  File "/Library/AutoPkg/autopkglib/URLGetter.py", line 189, in execute_curl
    text=text,
  File "/Library/AutoPkg/Python3/Python.framework/Versions/Current/lib/python3.7/subprocess.py", line 512, in run
    output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command '['/usr/bin/curl', '--silent', '--show-error', '--no-buffer', '--dump-header', '-', '--speed-time', '30', '--location', '--url', 'http://yellowmug.com/download/EasyCrop_2.4.5.dmg', '--fail', '--output', '~/Library/AutoPkg/Cache/com.github.homebysix.download.EasyCrop/downloads/tmppndv18x4']' returned non-zero exit status 22.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Library/AutoPkg/autopkglib/__init__.py", line 673, in process
    self.env = processor.process()
  File "/Library/AutoPkg/autopkglib/__init__.py", line 480, in process
    self.main()
  File "/Library/AutoPkg/autopkglib/URLDownloader.py", line 328, in main
    raw_headers = self.download_with_curl(curl_cmd)
  File "/Library/AutoPkg/autopkglib/URLGetter.py", line 197, in download_with_curl
    proc_stdout, proc_stderr, retcode = self.execute_curl(curl_cmd, text)
  File "/Library/AutoPkg/autopkglib/URLGetter.py", line 192, in execute_curl
    raise ProcessorError(e)
autopkglib.ProcessorError: Command '['/usr/bin/curl', '--silent', '--show-error', '--no-buffer', '--dump-header', '-', '--speed-time', '30', '--location', '--url', 'http://yellowmug.com/download/EasyCrop_2.4.5.dmg', '--fail', '--output', '~/Library/AutoPkg/Cache/com.github.homebysix.download.EasyCrop/downloads/tmppndv18x4']' returned non-zero exit status 22.
  File "/Library/AutoPkg/autopkglib/__init__.py", line 673, in process
    self.env = processor.process()
Command '['/usr/bin/curl', '--silent', '--show-error', '--no-buffer', '--dump-header', '-', '--speed-time', '30', '--location', '--url', 'http://yellowmug.com/download/EasyCrop_2.4.5.dmg', '--fail', '--output', '~/Library/AutoPkg/Cache/com.github.homebysix.download.EasyCrop/downloads/tmppndv18x4']' returned non-zero exit status 22.
Failed.
Receipt written to ~/Library/AutoPkg/Cache/com.github.homebysix.download.EasyCrop/receipts/EasyCrop.download-receipt-20200128-110930.plist

The following recipes failed:
    EasyCrop.download.recipe
        Error in com.github.homebysix.download.EasyCrop: Processor: URLDownloader: Error: Command '['/usr/bin/curl', '--silent', '--show-error', '--no-buffer', '--dump-header', '-', '--speed-time', '30', '--location', '--url', 'http://yellowmug.com/download/EasyCrop_2.4.5.dmg', '--fail', '--output', '~/Library/AutoPkg/Cache/com.github.homebysix.download.EasyCrop/downloads/tmppndv18x4']' returned non-zero exit status 22.

The following recipes have deprecation warnings:
    Name               Warning
    ----               -------
    EasyCrop.download  ### This recipe has been deprecated. It may be removed soon. ###

And here's after:

% autopkg run -vv EasyCrop.download.recipe
Processing EasyCrop.download.recipe...
WARNING: EasyCrop.download.recipe is missing trust info and FAIL_RECIPES_WITHOUT_TRUST_INFO is not set. Proceeding...
DeprecationWarning
{'Input': {}}
DeprecationWarning: ### This recipe has been deprecated. It may be removed soon. ###
{'Output': {'deprecation_summary_result': {'data': {'name': 'EasyCrop.download',
                                                    'warning': '### This '
                                                               'recipe has '
                                                               'been '
                                                               'deprecated. It '
                                                               'may be removed '
                                                               'soon. ###'},
                                           'report_fields': ['name', 'warning'],
                                           'summary_text': 'The following '
                                                           'recipes have '
                                                           'deprecation '
                                                           'warnings:'}}}
SparkleUpdateInfoProvider
{'Input': {'appcast_url': 'https://yellowmug.com/easycrop/appcast.xml'}}
SparkleUpdateInfoProvider: Version retrieved from appcast: 2.4.5
SparkleUpdateInfoProvider: Found URL http://yellowmug.com/download/EasyCrop_2.4.5.dmg
{'Output': {'url': 'http://yellowmug.com/download/EasyCrop_2.4.5.dmg',
            'version': '2.4.5'}}
URLDownloader
{'Input': {'filename': 'EasyCrop-2.4.5.dmg',
           'url': 'http://yellowmug.com/download/EasyCrop_2.4.5.dmg'}}
URLDownloader: No value supplied for prefetch_filename, setting default value of: False
URLDownloader: No value supplied for CHECK_FILESIZE_ONLY, setting default value of: False
Command '['/usr/bin/curl', '--silent', '--show-error', '--no-buffer', '--dump-header', '-', '--speed-time', '30', '--location', '--url', 'http://yellowmug.com/download/EasyCrop_2.4.5.dmg', '--fail', '--output', '~/Library/AutoPkg/Cache/com.github.homebysix.download.EasyCrop/downloads/tmpwojz01wl']' returned non-zero exit status 22.
Failed.
Receipt written to ~/Library/AutoPkg/Cache/com.github.homebysix.download.EasyCrop/receipts/EasyCrop.download-receipt-20200128-112006.plist

The following recipes failed:
    EasyCrop.download.recipe
        Error in com.github.homebysix.download.EasyCrop: Processor: URLDownloader: Error: Command '['/usr/bin/curl', '--silent', '--show-error', '--no-buffer', '--dump-header', '-', '--speed-time', '30', '--location', '--url', 'http://yellowmug.com/download/EasyCrop_2.4.5.dmg', '--fail', '--output', '~/Library/AutoPkg/Cache/com.github.homebysix.download.EasyCrop/downloads/tmpwojz01wl']' returned non-zero exit status 22.

The following recipes have deprecation warnings:
    Name               Warning
    ----               -------
    EasyCrop.download  ### This recipe has been deprecated. It may be removed soon. ###

Here's the diff: