electrum: Cannot upgrade or install new versions in linux

Command: sudo apt-get install python3-setuptools python3-pyqt5 python3-pip

• works fine - all install.

Command: sudo python3 -m pip install https://download.electrum.org/3.3.2/Electrum-3.3.2.tar.gz#egg=electrum[fast]

Result:

The directory '/home/fred/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
The directory '/home/fred/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Collecting electrum[fast] from https://download.electrum.org/3.3.2/Electrum-3.3.2.tar.gz#egg=electrum[fast]
  Downloading https://download.electrum.org/3.3.2/Electrum-3.3.2.tar.gz (8.9MB)
    100% |████████████████████████████████| 8.9MB 133kB/s 
    Complete output from command python setup.py egg_info:
    Error: Electrum requires Python version >= 3.6.1...
    
    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-osck464i/electrum/
You are using pip version 8.1.1, however version 18.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

Using sudo -H as suggested changes nothing. Using “pip install --upgrade pip” as suggested:

/usr/local/lib/python2.7/dist-packages/pip-18.1-py2.7.egg/pip/_vendor/requests/__init__.py:83: RequestsDependencyWarning: Old version of cryptography ([1, 2, 3]) may cause slowdown.
  warnings.warn(warning, RequestsDependencyWarning)
Requirement already up-to-date: pip in /usr/local/lib/python2.7/dist-packages/pip-18.1-py2.7.egg (18.1)

… and nothing changes trying to install after that

Trying to run or install from sources: Command: python3 run_electrum Output:

File "run_electrum", line 53
    sys.exit(f"Error: {str(e)}. Try 'sudo python3 -m pip install <module-name>'")
                                                                               ^
SyntaxError: invalid syntax

Command: sudo python3 -m pip install .[fast] Output:

Processing /home/fred/Electrum-3.3.2
    Complete output from command python setup.py egg_info:
    Error: Electrum requires Python version >= 3.6.1...
    
    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-wrs8v_10-build/
You are using pip version 8.1.1, however version 18.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.