crashes on start: ModuleNotFoundError: No module named 'gtts'

[themusicgod1]

running mnemosyne, after upgrading to focal:

themusicgod1@eva1:~$ mnemosyne
Log body:
 An unexpected error has occurred.
Please forward the following info to the developers:

Traceback (innermost last):
  File "/usr/bin/mnemosyne", line 268, in <module>
    mnemosyne.initialise(data_dir=data_dir, filename=filename,
  File "/usr/lib/python3/dist-packages/mnemosyne/libmnemosyne/__init__.py", line 400, in initialise
    self.register_components()
  File "/usr/lib/python3/dist-packages/mnemosyne/libmnemosyne/__init__.py", line 465, in register_components
    importlib.import_module(module_name), class_name)
  File "/usr/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/usr/lib/python3/dist-packages/mnemosyne/libmnemosyne/pronouncers/google_pronouncer.py", line 5, in <module>
    from gtts import gTTS
 ModuleNotFoundError: No module named 'gtts'

An unexpected error has occurred.
Please forward the following info to the developers:

Traceback (innermost last):
  File "/usr/bin/mnemosyne", line 268, in <module>
    mnemosyne.initialise(data_dir=data_dir, filename=filename,
  File "/usr/lib/python3/dist-packages/mnemosyne/libmnemosyne/__init__.py", line 400, in initialise
    self.register_components()
  File "/usr/lib/python3/dist-packages/mnemosyne/libmnemosyne/__init__.py", line 465, in register_components
    importlib.import_module(module_name), class_name)
  File "/usr/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/usr/lib/python3/dist-packages/mnemosyne/libmnemosyne/pronouncers/google_pronouncer.py", line 5, in <module>
    from gtts import gTTS
 ModuleNotFoundError: No module named 'gtts'
An unexpected error has occurred.
Please forward the following info to the developers:

Traceback (innermost last):
  File "/usr/bin/mnemosyne", line 268, in <module>
    mnemosyne.initialise(data_dir=data_dir, filename=filename,
  File "/usr/lib/python3/dist-packages/mnemosyne/libmnemosyne/__init__.py", line 400, in initialise
    self.register_components()
  File "/usr/lib/python3/dist-packages/mnemosyne/libmnemosyne/__init__.py", line 465, in register_components
    importlib.import_module(module_name), class_name)
  File "/usr/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/usr/lib/python3/dist-packages/mnemosyne/libmnemosyne/pronouncers/google_pronouncer.py", line 5, in <module>
    from gtts import gTTS
 ModuleNotFoundError: No module named 'gtts'

themusicgod1@eva1:~$ apt-cache policy mnemosyne
mnemosyne:
  Installed: 2.7.1+ds-1
  Candidate: 2.7.1+ds-1
  Version table:
 *** 2.7.1+ds-1 500
        500 http://mirrors.layeronline.com/ubuntu focal/universe amd64 Packages
        500 http://mirrors.layeronline.com/ubuntu focal/universe i386 Packages
        100 /var/lib/dpkg/status

Ubuntu: 20.04 LTS focal

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: mnemosyne 2.7.1+ds-1
ProcVersionSignature: Ubuntu 5.4.0-26.30-lowlatency 5.4.30
Uname: Linux 5.4.0-26-lowlatency x86_64
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Sun Apr 26 04:12:03 2020
InstallationDate: Installed on 2017-04-18 (1103 days ago)
InstallationMedia: Ubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
PackageArchitecture: all
SourcePackage: mnemosyne
UpgradeStatus: Upgraded to focal on 2020-04-25 (0 days ago)

[themusicgod1 (themusicgod1)]

Looks like it needs a runtime dependency on python3-gtts - installed python3-gtts and mnemosyne started no problem.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Ansgar Bohmann (ansgar-bohmann)]

I can both confirm the problem itself as well as the fix mentioned in #2. It's just a missing dependency and simply installing python3-gtts fixes the problem.

[Ansgar Bohmann (ansgar-bohmann)]

Two day ago I had confirmed both the bug and workaround on Ubuntu 20.04 (Focal Fossa).

Meanwhile I upgraded to 20.10 (Groovy Gorilla) and can confirm the same behaviour there as well. If python3-gtts is not manually installed, mnemosyne crashes on startup with the reported message. After manual installation of python3-gtts, everything works as expected.