Cannot allocate memory error during resolving dependencies

2019-07-30 11:11:41,999 ERROR:dependency.py:68(15217): Failed to resolve dependencies
ESC[31mTraceback (most recent call last):
  File "/home/vmbuilder/qt-ci/src/dependency.py", line 63, in get_submodule_dependencies
    resolvedRepositories = await self._resolve_repositories(modules, superRepo)
  File "/home/vmbuilder/qt-ci/src/dependency.py", line 111, in _resolve_repositories
    dependency_repo._declared_dependencies = await self._get_declared_dependencies_and_fill_sha1(dependency_repo, modules, superRepo, submodules)  # type: ignore
  File "/home/vmbuilder/qt-ci/src/dependency.py", line 174, in _get_declared_dependencies_and_fill_sha1
    await self.repoManager.resolveRepository(module)
  File "/home/vmbuilder/qt-ci/src/repositorymanager.py", line 218, in resolveRepository
    repositoryState.contentSha1 = repositoryState.contentSha1 or await self.root_tree(repositoryState.gerritInstance, repositoryState.project, repositoryState.sha1)
  File "/home/vmbuilder/qt-ci/src/utils.py", line 259, in async_lru_cached_wrapper
    result = await future_result
  File "/home/vmbuilder/qt-ci/src/repositorymanager.py", line 124, in root_tree
    show = await git.show("--no-patch", "--format=%T", sha1)
  File "/home/vmbuilder/qt-ci/src/repositorymanager.py", line 232, in __call__
    return await self.git(*args, **kwargs)
  File "/home/vmbuilder/qt-ci/src/ash.py", line 133, in __call__
    loop=_loop)
  File "/usr/lib/python3.6/asyncio/subprocess.py", line 225, in create_subprocess_exec
    stderr=stderr, **kwds)
  File "/usr/lib/python3.6/asyncio/base_events.py", line 1200, in subprocess_exec
    bufsize, **kwargs)
  File "/usr/lib/python3.6/asyncio/unix_events.py", line 200, in _make_subprocess_transport
    **kwargs)
  File "/usr/lib/python3.6/asyncio/base_subprocess.py", line 39, in __init__
    stderr=stderr, bufsize=bufsize, **kwargs)
  File "/usr/lib/python3.6/asyncio/unix_events.py", line 706, in _start
    universal_newlines=False, bufsize=bufsize, **kwargs)
  File "/usr/lib/python3.6/subprocess.py", line 709, in __init__
    restore_signals, start_new_session)
  File "/usr/lib/python3.6/subprocess.py", line 1275, in _execute_child
    restore_signals, start_new_session, preexec_fn)
OSError: [Errno 12] Cannot allocate memoryESC[0m
2019-07-30 11:11:42,078 ERROR:workitemfactory.py:650(15217): Creation of work items failed
ESC[31mTraceback (most recent call last):
  File "/home/vmbuilder/qt-ci/src/workitemfactory.py", line 614, in _testChange
    raise Exception(result.errorMessage)
Exception: [Errno 12] Cannot allocate memoryESC[0m
2019-07-30 11:11:42,084 DEBUG:scheduler.py:226(15217): Cancelling 1564484996
2019-07-30 11:11:42,086 DEBUG:workitem.py:317(15217): Work item (buildKey: 1564484996) changed state from New to Cancelled
2019-07-30 11:11:42,119 DEBUG:workitem.py:1143(15217): Final item ends because of cancellation: 1564484996
2019-07-30 11:11:42,298 DEBUG:workitem.py:317(15217): Work item (buildKey: 1564484996) changed state from Cancelled to Done