Can not generate Pipfile.lock by installing packages with requirementx.txt on Python 2.7

[adhh852]

Describe the issue briefly here.
Run: $pipenv install -r requirements.txt
Got error:
Creating a virtualenv for this project...
Pipfile: /home/ec2-user/test/Pipfile
Using /usr/bin/python2.7 (2.7.14) to create virtualenv...
⠋Already using interpreter /usr/bin/python2.7
New python executable in /home/ec2-user/.local/share/virtualenvs/test-LVXQY0Nl/bin/python2.7
Also creating executable in /home/ec2-user/.local/share/virtualenvs/test-LVXQY0Nl/bin/python
Installing setuptools, pip, wheel...done.
Setting project for test-LVXQY0Nl to /home/ec2-user/test

Virtualenv location: /home/ec2-user/.local/share/virtualenvs/test-LVXQY0Nl
Creating a Pipfile for this project...
Requirements file provided! Importing into Pipfile...
Traceback (most recent call last):
File "/usr/local/bin/pipenv", line 11, in
sys.exit(cli())
File "/usr/local/lib/python2.7/site-packages/pipenv/vendor/click/core.py", line 722, in call
return self.main(*args, **kwargs)
File "/usr/local/lib/python2.7/site-packages/pipenv/vendor/click/core.py", line 697, in main
rv = self.invoke(ctx)
File "/usr/local/lib/python2.7/site-packages/pipenv/vendor/click/core.py", line 1066, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "/usr/local/lib/python2.7/site-packages/pipenv/vendor/click/core.py", line 895, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/usr/local/lib/python2.7/site-packages/pipenv/vendor/click/core.py", line 535, in invoke
return callback(*args, **kwargs)
File "/usr/local/lib/python2.7/site-packages/pipenv/cli.py", line 416, in install
selective_upgrade=selective_upgrade,
File "/usr/local/lib/python2.7/site-packages/pipenv/core.py", line 1854, in do_install
import_requirements(r=project.path_to(requirements), dev=dev)
File "/usr/local/lib/python2.7/site-packages/pipenv/core.py", line 228, in import_requirements
project.recase_pipfile()
File "/usr/local/lib/python2.7/site-packages/pipenv/project.py", line 766, in recase_pipfile
if self.ensure_proper_casing():
File "/usr/local/lib/python2.7/site-packages/pipenv/project.py", line 802, in ensure_proper_casing
casing_changed = self.proper_case_section(pfile.get('packages', {}))
File "/usr/local/lib/python2.7/site-packages/pipenv/project.py", line 826, in proper_case_section
self.register_proper_name(new_casing)
File "/usr/local/lib/python2.7/site-packages/pipenv/project.py", line 366, in register_proper_name
f.write('{0}\n'.format(name))
TypeError: write() argument 1 must be unicode, not str
/usr/local/lib/python2.7/site-packages/pipenv/_compat.py:108: ResourceWarning: Implicitly cleaning up <TemporaryDirectory '/tmp/pipenv-2ttppI-requirements'>
warnings.warn(warn_message, ResourceWarning)

Please run $ python -m pipenv.help, and paste the results here.

$ python -m pipenv.help output

Pipenv version: '2018.6.25'

Pipenv location: '/usr/local/lib/python2.7/site-packages/pipenv'

Python location: '/usr/bin/python'

Other Python installations in PATH:

• 2.7: /usr/bin/python2.7

• 2.7: /usr/bin/python2.7

• 2.7.14: /usr/bin/python

PEP 508 Information:

{'implementation_name': 'cpython',
 'implementation_version': '0',
 'os_name': 'posix',
 'platform_machine': 'x86_64',
 'platform_python_implementation': 'CPython',
 'platform_release': '4.14.33-51.37.amzn1.x86_64',
 'platform_system': 'Linux',
 'platform_version': '#1 SMP Thu May 3 20:07:43 UTC 2018',
 'python_full_version': '2.7.14',
 'python_version': '2.7',
 'sys_platform': 'linux2'}

System environment variables:

• LC_CTYPE
• PYTHONDONTWRITEBYTECODE
• LESSOPEN
• SSH_CLIENT
• LOGNAME
• USER
• HOME
• PATH
• AWS_PATH
• LANG
• LESS_TERMCAP_se
• TERM
• SHELL
• EC2_AMITOOL_HOME
• LESS_TERMCAP_me
• LESS_TERMCAP_md
• LESS_TERMCAP_mb
• HISTSIZE
• AWS_ELB_HOME
• JAVA_HOME
• EC2_HOME
• AWS_AUTO_SCALING_HOME
• PIP_PYTHON_PATH
• _
• LESS_TERMCAP_ue
• SSH_CONNECTION
• AWS_CLOUDWATCH_HOME
• SSH_TTY
• OLDPWD
• HOSTNAME
• HISTCONTROL
• SHLVL
• PWD
• LESS_TERMCAP_us
• MAIL
• LS_COLORS

Pipenv–specific environment variables:

Debug–specific environment variables:

• PATH: /usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/opt/aws/bin:/home/ec2-user/.local/bin:/home/ec2-user/bin
• SHELL: /bin/bash
• LANG: en_US.UTF-8
• PWD: /home/ec2-user/test

---

Contents of Pipfile ('/home/ec2-user/test/Pipfile'):

[[source]]
url = "https://pypi.org/simple"
verify_ssl = true
name = "pypi"

[dev-packages]

[packages]
flask = "==0.10.1"
"jinja2" = "==2.7.3"
werkzeug = "==0.10"

[requires]
python_version = "2.7"

If you're on MacOS, just run the following:

$ python -m pipenv.help | pbcopy

---

Expected result

Describe what you expected.

Actual result

When possible, provide the verbose output (--verbose), especially for locking and dependencies resolving issues.